critical path methodology definition

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• Project management |
• Critical path method: How to use CPM fo ...

Critical path method: How to use CPM for project management

The critical path method is a technique that allows you to identify tasks that are necessary for project completion. The critical path in project management is the longest sequence of activities that must be finished on time to complete the entire project. Below, we break down the steps of how you can find the critical path for your next project.

Building out a project roadmap can help you visualize what needs to be done to reach your end goal. The critical path method helps you do exactly that. It’s a project management technique that involves mapping out key tasks or critical tasks necessary to complete a project. 

What is the critical path method (CPM)?

Also called critical path analysis (CPA), the critical path method (CPM) is a technique where you identify tasks that are necessary for project completion and determine scheduling flexibilities. A critical path in project management is the longest sequence of activities that must be finished on time in order for the entire project to be complete. Any delays in critical tasks will delay the whole project.

CPM revolves around discovering the most important tasks in the project timeline, identifying task dependencies, and calculating task durations.

CPM was developed in the late 1950s as a methodology to resolve the issue of increased costs due to inefficient scheduling. Since then, CPM has become popular for planning projects and prioritizing tasks. It helps you break down complex projects into individual tasks and gain a better understanding of the overall project flexibility.  

Why use critical path analysis?

CPA can provide valuable insight on how to plan projects, allocate resources, pace towards milestones, and schedule tasks. 

Here are some reasons why you should use the critical path method: 

Improves future planning: CPM can be used to compare expectations with actual progress. The data used from current projects can inform future project plans. 

Facilitates more effective resource management : CPM helps project managers prioritize tasks, giving them a better idea of how to avoid resource constraints. 

Helps avoid bottlenecks: Bottlenecks in projects can result in lost valuable time. Plotting out project dependencies using a network diagram will give you a better idea of which activities can and can’t run in parallel, allowing you to schedule work accordingly.   

How to find a project's critical path

Finding the critical path involves identifying the longest path between the start and end of the project by comparing the duration of critical and non-critical tasks. Below is a breakdown of the steps, with examples. 

1. List activities

Use a work breakdown structure to list all the project activities or tasks required to produce the deliverables. The list of activities in the work breakdown structure serves as the foundation for the rest of the CPM.

For example, let’s say the marketing team is producing a new interactive blog post. Here are some tasks that might be in the work breakdown structure:

Once you have a high-level idea of everything that needs to be done, you can start identifying task dependencies for the whole project.

2. Identify dependencies

Based on your work breakdown structure, determine the tasks that are dependent on one another. This will also help you identify any work that can be done in parallel with other tasks.

Here are the task dependencies based on the example above:

Task B is dependent on A

Task C is dependent on B 

Tasks C and D can run in parallel

Task E is dependent on D

Task F is dependent on C, D, and E

The list of dependent tasks is referred to as an activity sequence, which will be used to determine the critical path. 

3. Create a network diagram

The next step is to turn the work breakdown structure into a network diagram, which is a flowchart displaying the chronology of critical path activities. Create a box for each task and use arrows to depict task dependencies. 

You’ll add other time-bound components to the network diagram until you have the general project schedule figured out. 

4. Estimate task duration

To calculate the critical path, the longest sequence of tasks, you first need to estimate the duration of each activity. 

To estimate the duration, try: 

Making educated guesses based on experience and knowledge

Estimating based on previous project data

Estimating based on industry standards

Alternatively, try using the forward pass and backward pass technique:

Forward pass: This is used to calculate earliest start time (ES) and earliest finish time (EF) by using a previously specified start date. ES is the highest EF value from immediate predecessors, whereas EF is ES + duration. The calculation starts with 0 at the ES of the first activity and proceeds through the schedule. Determining ES and EF dates allows for early allocation of resources to the project. 

Backward pass: This is used to calculate the latest start (LS) and latest finish (LF) dates. LS is LF - duration, whereas LF is the lowest LS value from immediate successors. The calculation starts with the last scheduled critical path activity and proceeds backward through the entire schedule.    

The early and late start and end dates can then be used to calculate float, or scheduling flexibility of each task. 

5. Calculate the critical path

Calculating the critical path can be done manually, but you can save time by using a critical path algorithm instead. 

Here are the steps to calculate the critical path manually:

Step 1: Write down the start and end times next to each activity.

The first activity has a start time of 0, and the end time is the duration of the activity.

The next activity’s start time is the end time of the previous activity, and the end time is the start time plus the duration.

Do this for all the activities.

Step 2: Look at the end time of the last activity in the sequence to determine the duration of the entire sequence. 

Step 3: The sequence of activities with the longest duration is the critical path.

Using the same example above, here’s what the critical path diagram might look like:

Once you have the critical path figured out, you can build the actual project schedule around it.

6. Calculate the float

Float, or slack, refers to the amount of flexibility of a given task. It indicates how much the task can be delayed without impacting subsequent tasks or the project end date. 

Finding the float is useful in gauging how much flexibility the project has. Float is a resource that should be used to cover project risks or unexpected issues that come up. 

Critical tasks have zero float, which means their dates are set. Tasks with positive float numbers belong in the non-critical path, meaning they may be delayed without affecting the project completion date. If you’re short on time or resources, non-critical tasks may be skipped. 

Calculating the float can be done with an algorithm or manually. Use the calculations from the section below to determine the total float and free float. 

Total float vs. free float

Here’s a breakdown of the two types of float:

Total float: This is the amount of time that an activity can be delayed from the early start date without delaying the project finish date or violating a schedule constraint. Total float = LS - ES or LF - EF 

Free float: This refers to how long an activity can be delayed without impacting the following activity. There can only be free float when two or more activities share a common successor. On a network diagram, this is where activities converge. Free float = ES (next task) - EF (current task)

There are a few good reasons why project managers benefit from having a good understanding of float:

It keeps projects running on time: Monitoring a project’s total float allows you to determine whether a project is on track. The bigger the float, the more likely you’ll be able to finish early or on time.  

It allows you to prioritize : By identifying activities with free float, you’ll have a better idea of which tasks should be prioritized and which ones have more flexibility to be postponed. 

It’s a useful resource: Float is extra time that can be used to cover project risks or unexpected issues that come up. Knowing how much float you have allows you to choose the most effective way to use it.

How to use the critical path method

Critical path methodology provides visibility into your project’s progress, allowing you to monitor tasks and their completion times. Below are some additional applications of CPM.

Compress schedules

Though not ideal, there are times when project deadlines may be pushed up. In those situations, there are two schedule compression techniques you can use: fast tracking and crashing.

Fast tracking: Look at the critical path to determine activities that can be performed simultaneously. Running parallel processes will speed up the overall duration. 

Crashing: This process involves allocating more resources to speed up activities. Before obtaining more resources, make sure that they are still within the project scope and let the stakeholders know of any changes.

Having the critical path plotted out can help you choose the appropriate strategy to meet updated deadlines.

Resolve resource shortages

Keep in mind that CPM doesn’t take resource availability into account. When there is a resource shortage, like an overbooked team member or a lack of equipment, you can use resource leveling techniques to solve the issue. 

These techniques aim to resolve resource overallocation issues and ensure that a project can be completed with the resources that are currently available. 

Resource leveling works by adjusting project start and end dates, so you may have to readjust the critical path or apply this technique to activities with float.

Compile data for future use

The schedule created from CPM is subject to change since you’re working with educated estimates for activity durations. You can compare the original critical path to the actual critical path as the project runs.

This data can be used as a reference to get more accurate task duration estimates for future projects. 

Critical path method vs. PERT

CPM and Program Evaluation and Review Technique (PERT) were both developed in the 1950s. PERT is used to estimate uncertainty around project activities by applying a weighted average of optimistic and pessimistic factors. It evaluates the amount of time needed to complete an activity. 

PERT uses three time estimates to find a range for the duration of an activity:

Most likely estimate (M)

Optimistic (O)

Pessimistic (P) 

The calculation for PERT is: Estimated time = (O + 4M + P) / 6

The main difference between PERT and CPM is their level of certainty around activity durations—PERT is used to estimate the time required to complete activities, whereas CPM is used when the activity durations are already estimated. 

Let’s see how the two techniques compare:

PERT manages uncertain project activities; CPM manages predictable project activities.

PERT focuses on meeting or minimizing project duration; CPM focuses on time-cost-trade offs.

PERT is a probabilistic model, and CPM is a deterministic model.

PERT has three time estimates for each activity; CPM has just one.

Differences aside, both PERT and CPM analyze the following components:

List of required tasks

Estimated duration for each task

Task dependencies

These two project management tools can be used in tandem to boost their effectiveness. You can use PERT to get more realistic estimates of task durations before proceeding to calculate the critical path and floats.  

Critical path method vs. Gantt chart

Gantt charts are horizontal bar charts that map out project activities, which can be tracked against a set timeline. Both CPM and Gantt charts show the dependencies between tasks. 

Let’s go over some differences between the two tools:

Visualizes critical and non-critical paths and calculates project duration

Displayed as network diagram with linked boxes

Doesn’t show resources required

Plots critical path activities on a network diagram without timescale

Gantt chart

Visualizes how project activities are progressing

Displayed as horizontal bar chart

Shows resources required for each activity 

Plots critical path activities on a timescale 

Gantt charts can be paired with CPM to track critical paths over time and keep your project running on schedule. 

Use your project’s critical path for better project management

CPM can be a useful asset in project management, particularly for planning tasks and managing resource constraints. With the help of project planning tools, you’ll be able to create schedules and track projects with ease. To further increase your work efficiency, check out these 12 tips to be more productive today.

FAQ: Critical path method

What is the critical path formula.

The critical path formula consists of two parts: the forward pass and the backward pass. The forward pass calculates the earliest start times (ES) and finish times (EF) for each activity, with EF determined by adding the activity's duration (t) to its ES.

EF = ES + t (the duration of an activity)

The backward pass determines the latest start times (LS) and finish times (LF), setting the LF of the final activity equal to its EF and finding the LS by subtracting the activity's duration from its LF.

LF – t (the duration of an activity)

How do you calculate the critical path in a project schedule?

To calculate the critical path in a project schedule, you first identify all possible paths through the project's activity network. Then, for each path, you sum the durations of all activities. The longest path is the critical path. This requires calculating the earliest and latest start and finish times for each activity.

What is a CPM schedule?

A CPM schedule identifies critical and non-critical tasks to prevent delays by focusing on the longest sequence of dependent tasks to calculate the shortest project duration.

When can you use the critical path method?

You can use CPM during the planning phase of a project to identify the longest sequence of dependent tasks and calculate the shortest possible completion time. CPM is particularly useful for optimizing schedules for complex projects with multiple activities, milestones, and task dependencies.

Related resources

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Understanding dependencies in project management

Program manager vs. project manager: Key differences to know

15 project management interview questions, answers, and tips

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Critical Path Method (CPM) in Project Management

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What Is the Critical Path In Project Management?

What is the critical path method (cpm), cpm vs. pert, when should you use critical path analysis, what is the importance of cpm in project management, critical path diagram, critical path method (cpm) formula, critical path method example, critical path method steps.

• Benefits of Using CPM In Project Management

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Cpm & project management software, must-have features of critical path software.

• How to Find the Critical Path with ProjectManager

In project management, the critical path is the longest sequence of tasks that must be completed to execute a project. The tasks on the critical path are called critical activities because if they’re delayed, the whole project completion will be delayed. To find the critical path, project managers use the critical path method (CPM).

The critical path method (CPM) is a project management technique that’s used by project managers to create an accurate project schedule . The CPM method, also known as critical path analysis (CPA), consists in using the CPM formula and a network diagram to visually represent the task sequences of a project. Once these task sequences or paths are defined, their duration is calculated to identify the critical path.

Related: 12 Free Project Scheduling Templates for Excel

Finding the critical path is very helpful for project managers because it allows them to:

• Accurately estimate the total project duration.
• Estimate the time that’s necessary to complete each project task.
• Identify critical activities which must be completed on time and require close supervision.
• Find out which project tasks can be delayed without affecting the project schedule by calculating slack for each task.
• Identify task dependencies, resource constraints and project risks.
• Prioritize tasks and create realistic project schedules.

Once done by hand, the critical path can now be calculated automatically with project scheduling software equipped with Gantt charts , which makes the CPM method much easier. ProjectManager is project management software that helps you quickly implement the critical path method. Build a project schedule on our award-winning Gantt chart, then simply filter for the critical path. When it’s time to execute, your team can collaborate with a task list, kanban board or calendar. And you can track everything with dashboards and reports to ensure you stay on track. Get started today absolutely free.

ProjectManager can calculate the critical path for you on our award-winning Gantt charts— learn more .

The critical path method was developed in the late 1950s by Morgan R. Walker and James E. Kelley. The origins of the critical path method are closely related to the Program Evaluation and Review Technique (PERT), a similar method that is commonly used in conjunction with CPM in project management .

The critical path method (CPM) and program evaluation and review technique (PERT) are both project scheduling techniques. But they aren’t interchangeable. We’ve been talking about CPM, but before we compare it to PERT let’s define the term.

PERT is used to get accurate time estimates for complicated projects. It uses an algorithm to calculate the estimated duration for unpredictable activities. It focuses on events and milestones on a PERT chart with nodes in the wireframe when developing projects.

However, while these are two different techniques, PERT and CPM can be used together for project planning and scheduling. The difference between them lies in that PERT is about time planning and time management, while CPM is about time and budgeting. PERT delivers a project quickly and CPM gets the project done on budget and on time.

Now that we know what’s the critical path of a project, we can learn about the critical path method (CPM), an important project management technique that’s based on this concept.

Critical path analysis is another way of referring to the critical path method. As noted, it’s used by industries with complex projects, such as aerospace, defense, construction and product development.

Therefore, critical path analysis is a crucial first step in developing a project schedule. It’s done early in the life cycle of a project, usually in the planning phase , but it’s not unheard of to have CPM as part of a project proposal before the project has been approved.

By understanding which are the critical tasks in a project you can focus on getting those done if time, resources and costs are an issue. Knowing this in advance of executing a project will help you deliver that project successfully.

Related: Free Project Plan Template

Projects are made up of tasks that have to adhere to a schedule in order to meet a timeline. It sounds simple, but without mapping the work, your project scope can quickly get out of hand and you’ll find your project off track.

Using the critical path method is important when managing a project because it identifies all the tasks needed to complete the project. It then determines the tasks that must be done on time, those that can be delayed if needed and how much float or slack you have.

When done properly, critical path analysis can help you:

• Identify task dependencies, resource constraints and project risks
• Accurately estimate the duration of each task
• Prioritize tasks based on their float or slack time, which helps with project scheduling and resource allocation
• Identify critical tasks that have no slack and ensure those are completed on time
• Monitor your project progress and measure schedule variance
• Use schedule compression techniques like crash duration or fast tracking

As you can see in this critical path diagram, project activities are represented by letters and the critical path is highlighted in green. Tasks F, G and H are non-critical activities with float or slack. We can also identify task dependencies between the critical path activities, and also between activities (A, F and G) or (A, H and E), which are parallel tasks.

Before we learn how to use the CPM formula, we need to understand some key CPM concepts.

• Earliest start time (ES): This is simply the earliest time that a task can be started in your project. You cannot determine this without first knowing if there are any task dependencies
• Latest start time (LS): This is the very last minute in which you can start a task before it threatens to delay your project timeline
• Earliest finish time (EF): The earliest an activity can be completed, based on its duration and its earliest start time
• Latest finish time (LF): The latest an activity can be completed, based on its duration and its latest start time
• Float: Also known as slack, float is a term that describes how long you can delay a task before it impacts its task sequence and the project schedule. The tasks on the critical path have zero float because they can’t be delayed

The critical path method formula has two parts; a forward pass and a backward pass.

Forward Pass in CPM

Use the CPM diagram and the estimated duration of each activity to determine their earliest start (ES) and earliest finish (EF). The ES of an activity is equal to the EF of its predecessor, and its EF is determined by the CPM formula EF = ES + t (t is the activity duration). The EF of the last activity identifies the expected time required to complete the entire project.

Backward Pass in CPM

Begins by assigning the last activity’s earliest finish as its latest finish. Then the CPM formula to find the LS is LS = LF – t (t is the activity duration). For the previous activities, the LF is the smallest of the start times for the activity that immediately follows.

Let’s take a look at a critical path example to better understand how the critical path method is used in project management. Although it’s high-level, it can help you visualize the meaning of a CPM schedule .

We’ll use this critical path diagram to explain the elements that make up the critical path analysis process. To keep things simple, we’ve already done the calculations for this example using the CPM formula.

The above critical path method example shows the critical path for getting a website online. All the tasks that are scheduled to build and launch the website are shown in the rectangular nodes.

Some of the tasks are being done at the same time as others. For example, the work on defining a target market is being done as the design is being done and the content for the site is being drafted.

However, not all these tasks are equally important. Some aren’t critical to getting the site live by the deadline. That’s where the critical path comes in. It has identified by the colored arrows all the tasks that must be done in order to complete the project plan on time.

Now that you know the key concepts of the critical path method, here’s how to calculate the critical path in 8 steps.

1. Collect Project Activities

Use a work breakdown structure to collect all the project activities that lead to the final deliverable.

2. Identify Task Dependencies

Determine which tasks are dependent on other tasks before they can begin. Use your judgment and your team members’ feedback. Failing to define task dependencies correctly makes the critical path method useless.

3. Create a Critical Path Diagram

A CPM diagram or network diagram , depicts the order of activities.

4. Estimate the Timeline

To use the critical path method, you’ll need to estimate the duration of each task. Use data from past projects and other sources of information such as subject matter experts.

5. Use the Critical Path Formula

The critical path uses an algorithm, also referred to as the CPM formula. That algorithm has two parts, the forward pass and the backward pass. The forward pass is determined by using the earliest start for each activity (ES) and the earliest finish (EF). The ES of an activity equals the EF of the one before it. The EF is calculated by EF = ES + t (the duration of an activity).

The backward pass assigns the last activity’s EF as its latest finish. Then use the CPM formula to find the LS, which is LF – t. For the activities before that, LF is the smallest of the start times for the next activity.

6. Identify the Critical Path

The activities with 0 float make up the critical path. All of these critical path activities are dependent tasks except for the first task in your CPM schedule. All project tasks with positive slack are parallel tasks to the critical path activities.

7. Revise During Execution

Continue to update the critical path diagram as you go through the project execution phase. These critical path analysis steps determine what tasks are critical and which can float, meaning they can be delayed without negatively impacting the project schedule. Now you have the information you need to plan the critical path schedule more accurately and have more of a guarantee you’ll meet your project deadline.

You also need to consider other changes or constraints that might change the project schedule. The more you can account for these unexpected events or risks, the more accurate your critical path schedule will be. If time is added to the project because of these constraints , that’s called a critical path drag, which is how much longer a project will take because of the task and constraint.

Benefits of Using CPM in Project Management

There are many reasons to use the critical path method. It’s a great project management tool to help you deliver your project on time and within budget , but we’ve already discussed that at length. Here are some other benefits of using CPM.

Critical Path Analysis Improves Team Communication

It fosters better communication within the project team . Everyone is involved in providing input and that brings the expertise of various project team members together for the better good of the project as a whole. This includes subcontractors, architects, electricians, construction managers, etc.

CPM Helps Prioritize Tasks

Naturally, having determined the critical path is going to help you prioritize your work. You know the tasks that must be done and that gives you wiggle room if there are issues with time or cost. You might not get every activity done, but you’ll get the ones finished that are critical to the project.

CPM & PERT Help Create Accurate Schedules

The critical path method will help you make a more accurate project schedule , especially when you use it in conjunction with PERT charts. You can estimate better and discover areas of risk and prepare to respond to them to avoid costly delays.

CPM & Gantt Charts Help Map Out Project Plans

Another benefit is the visual nature of CPM, especially when mapped on the timeline of a Gantt chart . Having a visual element to communicate the project schedule is always a plus. Not everyone absorbs information in the same way. Visual tools help teams better understand what’s expected of them and when it’s expected.

Do you still have questions about the critical path method? In this video, Jennifer Bridges PMP, explains how to find the critical path using a CPM diagram.

As stated, the critical path method (CPM) was first invented in the late 1950s. During those times, project scheduling software didn’t exist, and project managers had to calculate the critical path manually.

Fortunately, today there are many project management software alternatives that can help with the critical path process. Most of them use Gantt charts to represent CPM diagrams and calculate the critical path, but their feature sets vary greatly. One of the most commonly used project management software to identify the critical path is Microsoft Project . However, it has major drawbacks that make ProjectManager a better choice.

Here are some of the main features that you’ll need as a project manager to properly use the critical path method for your scheduling process.

Link Tasks and Avoid Bottlenecks

Tasks that are dependent on another need to be a part of your critical path calculation. There are four types: those that are start-start, start-stop, stop-start and stop-stop. By identifying these task dependencies , you can avoid bottlenecks later in the project.

Get a High-Level View of Your Progress

Dashboards are an essential feature for keeping track of critical path activities. They provide a window into the project’s performance and progress by collecting data and displaying it in graphs and charts that show various metrics, such as costs, tasks and more.

Make More Insightful Decisions

Keeping track of a project’s critical path as it’s executed is how you stay on track. But if the information you’re gathering is dated, then you’re always going to be playing catch up. With real-time data from a cloud-based CPM software, you’re always seeing the project as it currently is.

Know Your Project Variance

Schedules are always changing as the project is impacted by internal and external forces. To ensure you’re on target, you need to have project management software that’s collecting data and displaying project variance, so you can compare the actual progress against where you’ve planned to be.

Keep a Record of Your Plan

The critical path helps you plan the project, but once you’ve finalized the schedule, you need to set a baseline. This saves the schedule so you can compare it to your actual progress and know if you’re on time, behind or ahead. Any critical path software should have this feature.

See Deep Data on Performance

Reports serve two purposes. They take you deeper into the project and expose insightful data on project variance, timesheets and more, which helps you stay on track. Filtering the results and sharing the reports is a great communication tool for stakeholder presentations.

How to Find the Critical Path With ProjectManager

Figuring out the critical path by hand takes time, and it must be done throughout the project, which is why using project management software streamlines the process. ProjectManager is award-winning software that automates the critical path method process for you.

Our online Gantt chart filters for critical path, links dependent tasks and is integrated into a full project management software. Sign up for a free 30-day trial of our software and follow along to build a dynamic Gantt chart and automatically calculate your critical path in a few easy steps.

1. Start a Project With a Gantt Chart

Managing a project on Gantt charts allows you to both plan and schedule in one place. Add your tasks and their durations, and they’ll automatically appear on a project timeline, allowing you to see your whole project at once.

In the software, upload your tasks manually or upload a pre-existing spreadsheet. Add task descriptions, deadlines, priority, tabs and assign them to one or more team members. We also provide templates to help you get started.

2. Add Task Dependencies

In the software, connect your dependent tasks on the Gantt chart by dragging one onto the other. You’ll see a dotted line indicating that the tasks are linked, and you can then define the type of dependency it is.

3. Set the Project Baseline

Setting the baseline is possible when you’ve finished making your project schedule, complete with deadlines and costs. The baseline captures your data and uses it to compare against your actual progress.

On the Gantt chart, create your baseline for the project by adding the start date to the task and when it’s due to be completed. These planned start and end dates will be compared to your actual project data and show you whether you’re on target.

4. See the Critical Path

Easily find the critical path of your project by using our critical path filter. This helps you know what must be done to complete the project and shows if you’re experiencing any slippage.

5. See Your Overview With a Dashboard

Now that you’ve got your project planned out, viewing it from a dashboard is the best way to get a high-level view of your progress.

From the dashboard view, track if your project is proceeding as planned. Our dashboard monitors several project metrics, such as variance, tasks and more, automatically calculating your data to display it in easy-to-read charts and graphs.

6. Report on Progress

Reporting is crucial to pull data from your project and get and share insights into how it’s doing. Reports come in many varieties, which together provide a snapshot of the whole project’s performance.

Easily generate reports on the critical path, task progress, project status , costs and more in the software. We do the calculations for you, and you can filter the results to show just what you want to see. Our reporting feature is done automatically with one click.

ProjectManager is an online tool that gets real-time data to determine how accurate your planned schedule is to the actual one, so you can adjust immediately if necessary. See how it can help your project by taking this free 30-day trial.

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Critical Path Method Resources

• Critical Path Software
• Project Scheduling Software
• Gantt Chart Software
• Project Management Software
• Work Breakdown Structure (WBS) Template
• Gantt Chart Template
• Work Schedule Template
• Project Scope Template
• Top 10 Project Management Methodologies: An Overview
• 3 Free Tools for Making Network Diagrams
• Project Scheduling Guide
• The Ultimate Guide to Gantt Charts
• What Is a Work Breakdown Structure?
• PERT and CPM: Their Differences and How to Use Them Together

External Articles

• The ABCs of the Critical Path Method – Harvard Business Review
• Understanding the Basics of CPM Calculations – PMI
• What Is the Critical Path in Project Management? – Elmhurst University

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What Is a Critical Path Method in Project Management?

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With roots dating back to the 1960s, the critical path method (CPM) is a technique used during the initial project analysis, planning, and scheduling phases of project management. The process has changed over the years since its inception, and while the modern critical path method mirrors the original in many ways, there are noticeable differences. But what is critical path in project management? 

Critical path in project management is the sequence of tasks or activities that must be completed during the execution of a project, and the critical path method is a means of mapping out these activities. In this article, we will go into greater detail when answering the question of what critical path is in project management and how to implement CPM in the 21st century.

Why It Is Important to Identify a Project’s Critical Path

Critical path is a project management term that refers to the various project tasks and activities that are the most time-consuming. Once the critical path has been identified, the individual tasks along the critical path—known collectively as critical activities—are easily prioritized and delegated as needed.

The overall project timeline ultimately depends on the critical path. Since the critical path represents the minimum amount of time needed to complete the project, it is vital to identify the critical path during the initial project planning phase.

How to Use the Critical Path Method (+ Example)

To illustrate how to use the critical path method, we’ll be using it to plan an online press conference.

Step 1: List all project tasks

Critical path project management begins with a list of all the tasks and activities, as well as the various milestones and deliverables, associated with the project at hand. For small or short-term projects, these activities can easily be listed with a simple, multi-column chart.

When planning an online press conference, for example, you might split activities into various groups: one for guests, another to cover the format of the press conference itself, yet another for logistics planning, and one more for creating an online press kit for distribution to mainstream media outlets.

Larger projects, which could involve dozens or even hundreds of separate tasks, are best managed by using CPM alongside other tools, such as a Gantt chart, to keep everything running as smoothly as possible.

Step 2: Identify dependencies and estimates

Next, take the time to identify any task dependencies within your project. These are tasks that can’t be finished until another related activity is complete. Once you’ve identified and listed dependencies, it’s useful to provide estimates of how long each individual task is expected to take. It’s okay if you don’t know exactly; a rough estimate will suffice.

If you have a list of guests you hope to see at your upcoming press conference, one of your specific tasks will involve sending out invites, either through email or traditional mail. However, you can’t start sending invitations until you’ve created them. And once created, you still need to compile the contact information for each guest.

As such, the activity of sending out invitations is dependent on the separate tasks of creating invitations and collecting contact information. Some activities, like collecting contact details, aren’t dependent on any other tasks. Other activities might have several different dependencies, so it’s important to complete this process for every activity on your list.

Read more: Understanding Task Dependency Types in Project Management

Step 3: Use a network diagram that traces dependencies

Creating a simple network diagram is a helpful way of visualizing the different project activities and their dependencies. In most cases, a diagram can be created using individual boxes to represent each task or activity. Each dependency should ultimately point to all of the tasks that can be started once it is completed. While some activities will point to several other tasks, others might point to only one.

When diagramming complicated or long-term projects, consider using different colors for each dependency. This makes it easier to track specific tasks—and their critical activities—throughout the entire project lifecycle.

Step 4: Do a forward pass

Once you have your basic diagram created, it’s time to move through your diagram with a forward pass. Not only does this ensure the validity and accuracy of your diagram, but it also makes it easy to determine the duration of the entire project. Although we already made rough estimates of the time-to-completion for each specific activity, that doesn’t really cover the project as a whole.

In order to determine the project duration, we need to introduce to new variables to the diagram:

• Early start time (ES) : This is the earliest possible time that any given task can be started.
• Early finish time (EF) : Conversely, this is the earliest possible time that any given task can be completed or finished.

Calculating the ES of each task is a straightforward process. In our project management critical path example above, the first tasks that can possibly be started are those with no dependencies. As such, they have all an ES of 0, as they can be started on day 0. To determine the EF, add the activity’s estimated duration to the ES. If task 1 takes 0.5 days to complete, for example, then the EF is 0.5.

To add these variables to our diagram, put the ES in the upper-left corner of each task box and put the EF in the upper-right corner. When calculating the EF and ES of tasks that depend on earlier tasks, make sure to add the variables from the task’s dependencies too.

Task 3, for example, has an EF of 0.5; however, it can’t be started until tasks 1 and 2 are finished. Instead of adding the two together, we simply pick the highest EF. In this case, task 3 has an EF of 1 because of its own time (0.5 days to finish) and the EFs of the previous tasks. 

Step 5: Do a backward pass

Next, complete a backward pass. Again, this process introduces two new variables to the diagram:

• Latest start time (LS) : This is the latest possible time that a task can be started without causing delays throughout the entire project.
• Latest finish time (LF) : Likewise, this is the latest possible time that a task can be finished without causing delays throughout the entire project.

To determine the LF, start by copying the final task’s EF and pasting it as the LF. As you can see in the example above, task 11 has 6.5 for both its EF and its LF.

To determine the LS, simply subtract the task’s duration from its LF. Since task 11 has a duration of 0.5 and an LF of 6.5, its LS is 6. For dependencies, use task 11’s LS as the LF of any tasks that lead directly to it. Using our critical path example, this includes tasks 3, 5, and 10. To determine the LS of these earlier tasks, simply subtract their duration from task 11’s LF. If a task points to more than one other task, use the lower LS as that task’s LF.

Step 6: Find the critical path

In order to find the project’s critical path, follow the tasks that have the same EF and LF. In our example, this has us starting on task 6 and proceeding to tasks 8, 9, 10, and 11—this is the critical path.

Remember, only critical activities can extend the project’s duration. While failing to finish task 9 on time would delay the entire project, a slight delay in task 4 or 5 wouldn’t have much effect, as long as they’re all completed by their respective LFs.

Benefits of the Critical Path Method in Project Management

Critical path aids skilled and novice project managers alike in optimizing and streamlining the entire project lifecycle. But how exactly does it help?

Prioritizing tasks

The critical path method makes it easy to prioritize and delegate tasks. Critical activities should be given the highest priority, since the project ultimately depends on those for completion. Non-critical activities can then be scheduled around the completion of these other, more important tasks.

Anticipating and avoiding bottlenecks

The CPM also helps you anticipate and avoid bottlenecks in the workflow, especially when it comes to scheduling and resource planning. Identifying the tasks that take the longest time to complete at the very beginning of your project ultimately helps you plan ahead and make the necessary accommodations before it’s too late.

Identifying slack

Sometimes known as float , slack refers to the total number of days that a task can be delayed before it affects other activities within the project. To identify slack in individual tasks, subtract the task’s EF from the LF.

Limitations of the Critical Path Method in Project Management

As useful as the CPM is, the process isn’t perfect. It has flaws, disadvantages, and limitations project managers should keep in mind.

Resource dependencies

While the critical path method makes it easy to understand individual task dependencies, it doesn’t accommodate resource dependencies. For example, assigning one person to complete two different tasks. Since the second task can’t be started until the first one is finished, there could be unexpected delays in the project duration.

Scheduling interruptions

Holidays, system updates, and PTO could all increase the overall project duration. While you certainly can’t plan for unexpected interruptions, some, like regular holidays and scheduled vacation time, should be taken into account when determining your project’s overall duration.

The CPM is best used when planning and organizing smaller projects. Large or complicated projects with hundreds or even thousands of individual tasks quickly become too bulky to be of any real use.

Manual vs Automated Critical Path Mapping

For most projects, critical path mapping can be completed manually. Our example illustrated above walks you through the steps needed to create a network diagram and critical path map without the use of software automation. For those who want to save even more time, however, there are apps and utilities that can automate much of the process.

While every software solution offers its own combination of features and functionality, some of the common elements of CPM software include:

• Drag-and-drop interface for adding tasks and dependencies
• Customizable templates for individual tasks
• Automated identification of your project’s critical path
• Collaboration amongst teammates and stakeholders
• Milestone tracking and notification
• Automated analysis and updating of start dates, due dates, and task durations

Automated CPM software is ideal for small project teams that are regularly working on large or complicated projects. It can also be used by novice PMs to guide them through the critical path method during their next project.

Critical Path Method: A Great Method for Planning a Project Timeline

The critical path method is one of the easiest and most straightforward ways of planning, analyzing, and disseminating a project timeline for project teammates, clients, and stakeholders. In project management , mapping out critical path can be implemented by novices and PM veterans alike, and it’s a proven way to streamline the typical project lifecycle while making it easier to prioritize activities and track productivity.

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The Ultimate Guide to the Critical Path Method

By Kate Eby | April 30, 2015

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In this article, you’ll learn the meaning of the critical path method, and how this method is used in project management. We’ve interviewed leading experts to help explain the key advantages of the critical path method.

Included on this page, you’ll find the six steps in the critical path method , the easiest way to find the critical path , and the best critical path software to use with step-by-step instructions.

What Is the Critical Path Method (CPM)?

CPM is a step-by-step project management technique to identify activities on the critical path. The approach breaks a project into work tasks, displays them in a flow chart, and then calculates the project duration based on estimated time frames for each. It identifies tasks that are critical, time-wise.

The text, A Guide to the Project Management Body of Knowledge (PMBOK ® Guide), an internationally recognized collection of processes and knowledge areas accepted as best practice for the project management profession, defines the critical path as “the sequence of scheduled activities that determines the duration of the project.” It is the longest sequence of tasks in a project plan that must be completed on time in order for the project to meet its deadline. If there is a delay in any task on the critical path, then your whole project will be delayed. Although many projects have only one critical path, some projects may have multiple critical paths.

Dr. Larry Bennett , a civil engineer, project manager, and author of four books, including a guide on critical path written in 1978 and titled, “ Critical Path Precedence Networks ,” explains that the critical path method helps manage projects in two different ways: “It produces a planned schedule to guide the project team, and it forms the basis for tracking project schedule performance by comparing actual with planned task progress.”

The Critical Path Method According to Two Experts 

We asked two critical path users for the best way to explain it. Here's what they had to say:

"The critical path is just a fancy way of saying 'How long does each task take before you can finish the project? Use this information to figure out the project's end date.' If a task takes longer than anticipated, the end date is pushed back. There are some tasks that don't immediately impact the project's end date that can be pushed back for some time. There are a whole bunch of calculations that go into figuring out what-ifs, forecasting, and scheduling, but that's where project management software comes in and makes everyone's lives easier. "

Rachel Burger , Capterra Construction Twitter:  @CapterraBuilder

"Some of the activities must happen in parallel. For example, if you tried to make a fried breakfast by doing one task at a time, and one after the other, things would go wrong. The plates need to be warming while other activities are going on. The toast needs to be toasting while the sausages are frying, and at the same time the bacon and sausages are under the grill. The eggs need to be fried last. A critical path analysis is a diagrammatical representation of what needs to be done and when. Timescales and costs can be applied to each activity and resource." Terence Jackson , Ph.D and CEO/Managing Partner at WEpiphany LL

“To learn about combining CPM with PERT for more comprehensive scheduling option, see this guide to combining PERT and CPM .”

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Background & History of Critical Path

Dr. Bennett is no stranger to critical path. He has applied critical path scheduling to a wide variety of projects since 1965. He has also spent 29 years on the engineering faculty at the University of Alaska Fairbanks, teaching undergraduate and graduate courses in technical management, including project management and scheduling.

In addition to his books , he has written more than 50 professional papers and articles on topics ranging from construction management to network techniques for project scheduling. 

Dr. Bennett points out that critical path has come a long way. In fact, the original critical path method was done by hand. As Dr. Bennett describes it: 

“The original critical path method used arrows to represent tasks and tied them together by connecting their beginning and end at nodes, so that proper sequencing was developed. This approach persisted for a decade, when a different method, with the same results, became popular. Professor John W. Fondahl, a professor of construction management at Stanford University, proposed in a 1961 paper that each task be represented by a node – square, circle, or oval – and the nodes be tied together with lines or arrows representing the sequence between tasks. This approach, referred to as the activity-on-node (AON) or precedence method, caught on rapidly and has supplanted the earlier activity-on-arrow (AOA) method in nearly all uses.”

How the Critical Path Method Was Created 

Using the critical path method to schedule projects began in the late 1950s, with two simultaneous, unrelated projects. The US Navy’s Fleet Ballistic Missile (Polaris) Program was behind schedule and needed help resolving the problem. The suggested solution was to divide the project into several thousand tasks, represent each task by an arrow, connect the arrows in proper sequence, estimate the duration of each task, and calculate the project duration and the degree of schedule criticality of each task. 

At about the same time, the EI DuPont de Nemours Company, an American chemical company, was experiencing delays in its plant turnarounds, a project to rearrange production facilities for different products. They, too, needed help and the proposed answer was similar to that of the Polaris Program. 

The developers of the Polaris Program’s approach called their solution the Project Evaluation and Review Technique (PERT), while the DuPont method was called Critical Path Method (CPM).  Although these methods are similar, they used different techniques for estimating task duration. 

The PERT method used three different time estimations for each task duration and calculated the probability of project completion by any given time. The DuPont approach used one time duration for each task; it was concerned not only with project completion time, but also with analyzing the extra costs that would accrue if the project duration were decreased.  

Dr. Bennett says that today, “the terms PERT and CPM are used interchangeably, both meaning any network scheduling method and PERT having lost its inclusion of three time estimates and probabilities.”

The Everyday Advantages of Critical Path

Although it originated in the late 1950s, critical path is still incredibly important to project managers today. It provides a visual representation of project activities, clearly presents the time required to complete tasks, and tracks activities so you don’t fall behind. The critical path method also reduces uncertainty because you must calculate the shortest and longest time of completion of each activity. This forces you to consider unexpected factors that may impact your tasks and reduces the likelihood that an unexpected surprise will occur during your project.

According to Dr. Bennett, the critical path method also has three main benefits for project managers:

• Identifies the Most Important Tasks:  First, it clearly identifies the tasks that you will have to closely manage. If any of the tasks on the critical path take more time than their estimated durations, start later than planned, or finish later than planned, then your whole project will be affected. 
• Helps Reduce Timelines: Secondly, “if, after the initial analysis predicts a completion time, there is interest in completing the project in a shorter time frame, it is clear which task or tasks are candidates for duration reduction,” said Dr. Bennett. When the results from a critical path method are displayed as a bar chart, like a Gantt chart, it is easy to see where the tasks fall in the overall timeframe. You can visualize the critical path activities (they are usually highlighted), as well as task durations and their sequences. This provides a new level of insight into your project’s timeline, giving you more understanding about which task durations you can modify, and which must stay the same. 
• Compares Planned with Actual: And lastly, Dr. Bennett says the critical path method can also be used to compare planned progress with actual progress. “As the project proceeds, the baseline schedule developed from the initial critical path analysis can be used to track schedule progress.  Throughout a project, a manager can identify tasks that have already been completed, the predicted remaining durations for in-progress tasks, and any planned changes to future task sequences and durations.  The result will be an updated schedule, which, when displayed against the original baseline, will provide a visual means of comparing planned with actual progress.”

Experts Share the #1 Advantage of Critical Path   

"For me, the biggest advantage of the critical path method is that it makes risk assessment easy. If I’ve got dependencies laid out and plans change, it’s very easy to say, 'Because you missed that deadline, the next deliverable is going to be late by X days, and that puts us beyond our plan by Y days.' Simple. That said, I don’t think you have to fully adopt a method like critical path to do this on projects. It’s best to adopt the parts of any method that work for your project and your team—being adaptable as a PM will help you find true success."

Brett Harned,  digital project management consultant , writer, speaker, and community builder.

Twitter:  @BrettHarned 

"Two issues that continue to plague projects are the competing priorities of cross functional team members and distractions from 'noise' on the project.  With so much activity, the critical path enables a clear, pointed view of what must happen next and 'who is on the clock' for meeting project commitments."

Robert Kelly, co-founder of  @PMChat  and managing partner of  Kelly Solutions , a project management firm. 

Twitter:  @rkelly976

"I especially like the 'unintended benefits' critical path (CP) analysis brings, including discoveries of hidden dependencies and resource conflicts. CP analysis also often leads to better prioritization and redistribution of team-members.  And CP can expose the needs / opportunities for inserting lags / leads to further improve the schedule."

Jeff Furman, PMP, author of  "The Project Management Answer Book"

Twitter:  @PMAnswerBook  

"The critical path method brings an important level of clarity to your project. It is a visual depiction of the fragility of the balance of your constraints: If one of the activities on the path gets delayed, your project gets delayed. It is also a great way to determine where to invest resources if the project has fallen behind schedule."

Cesar Abeid,  host of the Project Management for the Masses Podcast

Key Steps in the Critical Path Method

There are six steps in the critical path method: 

Step 1: Specify Each Activity

Using the work breakdown structure, you need to identify each activity (or task) involved in the project. This activity specification list should only include higher-level activities. When detailed activities are used, the critical path analysis may become too complex to manage and maintain. 

A work breakdown structure breaks down projects into manageable sections. 

The first step is to identify the main deliverables of a project. Then you can start breaking down the high-level activities into smaller chunks of work. 

You can choose how to display your work breakdown structure. Some people use a tree structure, while others use lists or tables. An outline is one of the easiest ways to represent a work breakdown structure.

Step 2: Establish Dependencies (Activity Sequence)

Some activities will depend on the completion of others. Listing the immediate predecessors of each activity will help you identify the correct order. To correctly identify activities and their precedence, ask yourself these three questions for each activity on your list from step one: 

• Which task should take place before this task happens?
• Which tasks should be finished at the same time as this task?
• Which tasks should happen right after this task?

Step 3: Draw the Network Diagram  

Once you have identified the activities and their dependencies, you can draw the critical path analysis chart (CPA), known as the network diagram. The network diagram is a visual representation of the order of your activities based on dependencies.

This critical path diagram used to be drawn by-hand, but there are now software programs that can create this diagram for you. 

Step 4: Estimate Activity Completion Time

Using past experience or the knowledge of an experienced team member, you must now estimate the time required to complete each activity. If you are managing a smaller project, you will most likely estimate time in days. If you are working with a complex project, you may have to measure time in weeks.

If you don’t feel comfortable using your best-guess estimates, you can use the 3-point estimation method, which is designed to put more weight on the most realistic timeframe. 

In three-point estimation, you must come up with three time estimates for every task, based on prior experience or best guesses. The estimation method is presented in formulas in order to calculate the time duration more accurately. 

a = the best-case estimate m = the most likely estimate b = the worst-case estimate 

These three values identify what happens in an optimal state, what is the most likely, and what happens in the worst case scenario. 

Once you’ve identified these values, you can use them in two different formulas. The first is used to find the Weighted Average, which puts more weight on the “Most Likely” value. The formula is as below. E stands for Estimate, and the 4 and 6 represent the standard method to place more weight on the most realistic value. 

E = (a + 4m + b) / 6

The second way of using these values is known as Triangular Distribution. The main difference is that this method doesn’t put more weight on the “Most Likely” value. The formula is as below. E stands for Estimate, and the 3 represents the standard method.

E = (a + m + b)/3

Step 5: Identify the Critical Path   

There are two ways you can now identify the critical path. You can eyeball your network diagram and simply identify the longest path throughout the network -- the longest sequence of activities on the path. Be sure to look for the longest path in terms of longest duration in days, not the path with the most boxes or nodes. 

You can also identify critical activities with the Forward Pass/Backward Pass technique, identifying the earliest start and finish times, and the latest start and finish times for each activity. 

If you have multiple critical paths, you will run into network sensitivity. A project schedule is considered sensitive if the critical path is likely to change once the project begins. The more critical paths in a project, the higher the probability of a change in schedule. 

Step 6: Update the Critical Path Diagram to Show Progress 

As the project progresses, you will learn the actual activity completion times. The network diagram can then be updated to include this information (rather than continuing to use estimations).

By updating the network diagram as new information emerges, you may recalculate a different critical path. You will also have a more realistic view of the project completion due date and will be able to tell if you are on track or falling behind.

Other Scenarios in the Critical Path Method

One of the biggest benefits of the critical path method is identifying the crucial tasks that, if missed, will impact your project’s completion date. It will also provide visibility into your project’s status, allowing you to see if you are on track. 

Shortening Your Schedule

As you’re going through the critical path method, you may find that you want to intentionally shorten the duration of your project or that you need to compress your project schedule in order to meet the deadline. There are two ways to do this: fast tracking or crashing.

Fast Tracking 

In fast tracking, you look at the critical path and decide which activities can be done parallel to each other, to move the project along faster. You only need to review the activities on the critical path because all the other activities have float (if you shorten the duration of those activities, you’re only giving them more float). 

While fast tracking reduces your project timeframe, it also involves risk because you are performing parallel activities that were originally planned to be performed in sequence. 

Crash Duration 

Crash duration, or crashing, refers to the shortest possible time for which an activity can be scheduled. This happens by adding more resources to completing that certain activity. However, crashing the critical path results in lower quality of work because the goal in crash duration is speed.

Managing Resource Constraints 

As you manage your project, you may also run into resource constraint issues that could change the critical path. If you try to schedule certain activities at the same time, you may find that you need more people than are available. As a result, those activities will need to be rescheduled. Resource leveling is the process of resolving these conflicts. 

Resource Leveling and Expansion 

With resource leveling, you can resolve conflicts over allocating resources. A resource-leveled schedule may include delays due from resource bottlenecks (a resource being unavailable at the necessary time). 

Resource leveling may also result in a previously shorter path becoming the longest or most “resource critical” path. This happens when the tasks on the critical path are affected by resource constraints. 

A similar concept is called the critical chain, which protects activity and project durations from unexpected delays due to resource constraints. 

Assessing the Final Project

These scenarios demonstrate all the unexpected changes that can occur when managing a project, and how they can affect the critical path. While things are always subject to change, the good news is that you can measure the variance from your original project schedule and track how it impacted your final project. 

Flexibility and Assessing Delays

A schedule created from the critical path method naturally involves a lot of fluctuation because you have to use best-guess estimates to calculate time. If one mistake is made in activity completion time, your whole critical path schedule could change. Or, you may need to purposefully delay project activities due to resource constraints. 

Sorting out these delays and determining what caused them can help you avoid similar issues in the future. An important part of your post-project plan is the As Built Critical Path, which analyzes the specific causes and impacts of changes between the planned schedule and actual schedule implemented. The As-Built Critical Path is a schedule that shows the dates that the activities actually occurred and allocates time by determining the responsibility for the delays on the critical path. 

Critical Path Software

When the critical path method was first developed, you had to identify the critical path by hand, drawing the network diagram with “nodes” to present the stages of a project and connecting the nodes with arrows or “arcs.” 

However, drawing nodes, tables, and arrows can be a time-consuming, difficult task, especially when things are constantly changing at the beginning of a project.

Rather than relying on hand-draw diagrams, there are a number of project management software programs available today that will do the work for you and identify the critical path with the click of a button.

Here are two different tools with critical path features:

Find the Critical Path with Microsoft Project

You can display the critical path in the Gantt chart view of Microsoft Project.

First, you must enter all your tasks, their start and end dates, the duration of each task, and identify the predecessors. Then, you can adjust the view of your MS Project file to display the critical path.

• Click View > Gantt Chart.
• Click Format and then select the Critical Tasks check box.  

Tasks on the critical path now have red Gantt bars.

Identify Critical Path in Other Views

You can see the critical path in any task view by highlighting it.

• Click the View tab and select a view from the Task Views group.
• Staying within the View tab, click Critical from the Highlight list. The critical path shows up in yellow.
• To see only the tasks on the critical path, click the Filter arrow and select Critical .  

In a network diagram, tasks on the critical path automatically show up in red. No highlighting is needed.

See the Critical Path in a Master Project

Entire subprojects can be on the critical path when you’re managing a master project. To identify subprojects on the critical path, you can adjust Microsoft Project to treat the subprojects like summary tasks.

• Click File > Options .
• Select Schedule and then scroll down to the Calculation options for this project .  

Make sure the Inserted projects are calculated like summary tasks box is selected.

Change the Tasks on the Critical Path

Critical tasks typically have no slack. However, you can tell Microsoft Project to include tasks with one or more days of slack on the critical path, so you can identify any potential problems that may arise.

• Click Advanced , then scroll down to the Calculation options for this project area.
• Add a number to the Tasks are critical if slack is less than or equal to box.  

Identify the Critical Path in Seconds with Smartsheet

Smartsheet, a work management and collaboration tool in a spreadsheet layout, offers a pre-formatted Gantt chart template  to make it even easier to find the critical path.

With this pre-made Gantt chart template, complete with sections, sub-tasks, and sub-sub-tasks already formatted, all you need to do is enter your own project planning information. A Gantt chart will automatically be made for you, and with the click of a button, you can identify the critical path on the Gantt chart.

Here’s how to find the critical path in Smartsheet, using a Gantt chart template:

1. Choose a Gantt Chart Template

• Go to Smartsheet.com and login to your account (or start a free 30 day trial ).
• From the Home screen, click Create New and choose Browse Templates .
• Type “dependencies” in the Search Templates box and click the magnifying glass icon.
• Select the Basic Project with Gantt & Dependencies and click on the blue Use Template in the upper-right corner.
• Name your template, choose where to save it, and click the OK button.  

2. List Your Task Information

A pre-made, formatted template will open with sample content filled in for reference. This section is where you add your activities, or tasks, from your work breakdown structure. This is also where you can show the hierarchy, or relationship, between tasks.

The yellow cells at the top are there simply for instructional reference. To delete them, right-click on each yellow box and select Delete Row .

• Add your tasks under the Task Name column.
• Use the cells named Section 1, Section 2, and Section 3 to establish hierarchy (for more information on hierarchies, click here ).
• If you need to delete a row, right-click on the cell in the row you’d like to delete and select Delete Row .  

On the left side of each row, you can attach files directly to a task or start comments with a colleague about a task, adding more context to your project.

3. Provide Start and End Dates

Add start and end dates for each task. If you click and drag either end of a green task bar on the right in the Gantt view, Smartsheet will automatically change the matching dates in the task table.

• Select a cell in the Start Date or End Date column.
• Click on the calendar icon and choose a date.  

You can also manually enter a date in the cell. Smartsheet will automatically calculate the duration of each task for you.

4. Add % Complete and Assigned To Information

The % Complete and Assigned To columns provide more context around your project. In the Gantt view on the right side, you can quickly see how much of a task has been completed by the length of the thin grey bars inside the task bars.

The Assigned To column allows you to assign the task to a particular team member, providing visibility into who is doing what.

• In the % Complete column, enter the percentage of work complete for that task. Enter a whole number and Smartsheet will auto-fill the percentage sign.
• In the Assigned To column, choose a name from the drop-down menu or manually enter a new name.

5. Establish Predecessors

Predecessors are used to create dependencies between tasks (identifying which tasks need to happen before or after another task).

• On the far-left of the sheet, each row is assigned a number. In the Predecessor column, enter the row number that represents the row of the preceding task. This will create a link from the current row (the dependent task) to the specified row (the predecessor task).
• Enter the row numbers of all other predecessors in the Predecessor column.  

You can also create predecessor dependencies from the Gantt chart on the right. Drag the bottom, right-corner of a Gantt bar down to the Gantt bar of the task that should follow it. The Predecessor column will be automatically updated.

6. Identify the Critical Path

Now that you have created a Gantt chart in Smartsheet, you can identify the critical path on the Gantt chart with the click of a button.

• On the right side of the screen, where your Gantt chart is displayed, click the far-right button that depicts a critical path (the two red Gantt bars).
• On the Gantt chart, the tasks that are on the critical path will be outlined in red.  

How to Import a Microsoft Project File (.MPP) into Smartsheet

Smartsheet works with Microsoft Project, so if you already have your project planning information stored in Microsoft Project, you can easily import that directly to Smartsheet.

• Click the Home tab and click the grey Import button.
• Choose the Import MS Project File .  

• Click Select, choose the file you would like to import, and click Open .
• Click Continue and an Import Settings form appears. Select the row in the form that contains your column headers (it will probably be the first row) and click Import .
• The imported file will appear as a new sheet within Smartsheet. Click on the sheet name to open it.

Studying for the PMP® Exam? Here’s What You Need to Know about the Critical Path Method

To earn your Project Management Professional (PMP) ® credential, you need to pass the PMP exam, a 200-question, multiple choice test offered by the Project Management Institute (PMI).

Critical path is an important part of the PMP Exam and there will certainly be questions about it on the test. You’ll need to be able to draw a network diagram, identify the critical path, use the Forward Pass/Backward Pass technique, and calculate slack.

Here is an overview of the most important things to know about the critical path method to help you pass the PMP exam:

How to Draw a Network Diagram

On the PMP Exam, you will be asked to draw a network diagram. The exam will list all the activities in a project and will tell you when the activities can start. With that information, you’ll be asked to identify the critical path and its duration.

To explain how to draw a network diagram, Bennett has created a sample eight-task project:

• Design Tank Project (10 days) can start right away.
• Construct Tank Foundation (25 days) and Select Tank Supplier (8 days) can start as soon as Design Tank Project is finished.
• Manufacture Tank Components (10 days) can start as soon as Select Tank Supplier is finished.
• Deliver Tank to Jobsite (4 days) can start as soon as Manufacture Tank Components is finished.
• Prepare Installation Drawings (3 days) can start as soon as Select Tank Supplier is finished.
• Assemble Tank (15 days) can start as soon as Deliver Tank to Jobsite, Prepare Installation Drawings and Construct Tank Foundation are all finished.
• Test & Commission Tank (4 days) can start as soon as Assemble Tank is finished.
• After Test & Commission Tank is finished, the project is complete.  

To answer the question, you’ll need to draw a network diagram.

Here’s how:

• Draw a box and label it as your first activity (Design Tank Project). In the box, make sure to write the duration in days (in this case, it is 10 days).
• Begin your diagram by drawing the relationship between Design Tank Project, and Construct Tank Foundation and Select Tank Supplier. You can do this by drawing a box for the other activities, and drawing arrows to these boxes from Design Tank Project.
• Continue drawing boxes to represent activities, and arrows to represent when an activity can begin.  

After you have drawn the network diagram, you will be able to find the critical path. Remember: the critical path is the longest duration path throughout the network in days, not the path with the most boxes.

In this example, the critical path is Design Tank Project, Construct Tank Foundation, Assemble Tank, and Test & Commission Tank, with a total duration of 54 days.

You can identify the critical path by eyeballing the diagram to find the longest duration in days, or you could use the Forward Pass/Backward Pass Technique outlined in the next section.

How to Use the Forward Pass/Backward Pass Technique

The Forward Pass/Backward Pass technique is another way to find the critical path. It is best used when you have multiple branches, or multiple entry points, for an activity. 

You may also need to use the Forward Pass/Backward Pass technique if you are asked to identify the earliest start or finish times, or latest start or finish times, for an activity. Or, to find the slack (or float) for each activity.

Before you start using the Forward Pass/Backward Pass technique, here are some terms that you first need to understand:

• Earliest start time (ES): The earliest time an activity can start once the previous dependent activities are completed.
• Earliest finish time (EF): The earliest start time for the activity plus the time required to complete the activity (the earliest an activity can be completed).
• Latest finish time (LF): The latest time an activity can be completed without delaying the entire project.
• Latest start time (LS): The latest finish time minus the time required to complete the activity.

As you run the Forward Pass/Backward Pass technique through your network diagram, arrange each value according to the following legend (SL stands for slack, which we’ll cover in the next section).

How to Do the Forward Pass: Finding the Earliest Start Time and Finish Time

There are two formulas in the Forward Pass/Backward Pass technique. The first is the Forward Pass formula for you to use as you move from beginning to end in your network diagram (from your first activity to your last). This formula will find the earliest start time (ES) and the earliest finish time (EF) for each activity.

To start the Forward Pass, make the ES of the first task zero. For all other tasks, the ES is the same as its immediate predecessor’s EF.

Use this formula to calculate EF:

EF = ES + Duration

So, for Design Tank Project, the ES is zero and, the EF is 10 (10+ duration of 0). We also know that the ES for Select Tank Supplier is 10 and the EF is 18 (10 + duration of 8). Continue like this throughout the network diagram.

How to Do the Backward Pass: Finding the Latest Start Time and Finish Time

The second formula is for Backward Pass, when you are moving from the last activity to the first activity (you are moving backwards). This formula will find the latest start time (LS) and latest finish time (LF) for each activity.

To start the Backward Pass, make the last activities LF the same as its EF. For all other tasks, the LF is the same as its immediate predecessor’s LS.

Use this formula to calculate LS:

LS = LF - Duration

For the Test & Commission Tank, the LF is 54 and, the LS is 50 (54 - duration of 4). For Assemble Tank, the LF is also 50 and, the LS is 35 (50 - duration of 15 days). Continue this formula throughout the network diagram.

To check that you’ve done Backward Pass correctly, the first activity (Activity A) should have an LS (latest start time) of 0.

Here’s the completed Forward Pass/Backward Pass technique:

Two Rules to Remember for Forward Pass/Backward Pass

During the Forward Pass, if you find activities that join (multiple activities that flow into one activity), you must run the Forward Pass formula for each entry point and use the highest value from the formulas.

During the Backward Pass, if you have activities that join, you must run the formula for each entry point and use the lowest value.

How to Calculate Float or Slack on the PMP Exam

Now that you have calculated ES and LS for each activity, you can find the float (or slack).

The slack time, also known as float time, for an activity is the time between the earliest and latest start time. Critical activities, activities on the critical path, will always have zero slack.

There are two formulas to calculate slack based on the values you identified in the Forward Pass/Backward Pass technique.

Slack = LF - EF

Slack = LS - ES

You will have to use this process if you are asked to identify an activity’s slack on the PMP exam. Or, if you’re not sure which activities are on the critical path, you could find the slack of each activity, knowing that activities on the critical path always have zero slack.

The final figure below shows the slack values for each task. You can see that the four tasks on the critical path have zero slack -- Design Tank Project, Construct Tank Foundation, Assemble Tank, and Test & Commission Tank.

Key Critical Path Terms for the PMP Exam

Here are the most important terms related to the critical path method that you should understand before taking the PMP exam.

• Critical path method (CPM): The critical path method is a step-by-step project management technique for process planning that identifies critical and noncritical tasks, preventing timeframe problems and process bottlenecks.
• Critical Path DRAG (Devaux’s Removed Activity Gauge): The amount of time that an activity on the critical path is adding to the project’s duration. Or, alternatively, the amount of time the project completion date would be reduced by decreasing a critical path activity’s duration to zero.
• Criticality Index: Used in risk analysis, the Criticality Index shows how often a particular task was on the critical path during analysis. Tasks with a high Criticality Index are more likely to cause delay to the project since they’re more likely to be on the critical path.
• Earliest start time: The earliest time an activity can start once the previous dependent activities are completed.
• Earliest finish time: The earliest start time for the activity plus the time required to complete the activity.
• Latest finish time: The latest time an activity can be completed without delaying the entire project.
• Latest start time: The latest finish time minus the time required to complete the activity.
• Total float: The amount of time an activity can be delayed from its early start date without delaying the entire project.
• Free float: The amount of time an activity can be delayed without delaying the early start date of a successor activity.
• Forward pass: The process to determine the early start or early finish times for activities in the critical path method.
• Backward pass: The process to determine the late start or late finish times for activities in the critical path method.
• Network diagram: A schematic display of the relationships between project activities, always drawn from left to right to reflect the order of the project.
• Network analysis: The process of breaking down a complex project into components (activities, durations, etc) and plotting them to show their interdependencies and interrelationships.

The Easiest Way to Find the Critical Path

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*The Project Management Professional (PMP) and PMBOK Guide are registered marks of the Project Management Institute, Inc. ​

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What is the critical path method? Complete guide with examples

“It depends” is a phrase sometimes referred to as the classic product management answer — and it is! While we all would love a simple answer to many of life’s questions, there are often many factors at play which means, well, it depends!

One factor product managers have to consider in their answers is dependencies. These activities might not be in the direct control of the product team but are required as part of the product development effort for success. No matter how best companies structure themselves to minimize dependencies, often they still exist. Finding out which ones matter and which impact timelines the most can be challenging. That is where the critical path method (CPM) can help.

What is the critical path method (CPM)?

The critical path method (CPM) is a widely-used project management technique that helps plan and schedule complex projects. It is used to identify the critical path of a project, aka the sequence of activities that determines the minimum completion time of the project.

What does “critical path” mean?

A critical path is a sequence of “critical” activities in a project that must be completed on time for the project to be completed on schedule. These “critical” activities will also help you to determine the minimum completion time for the project.

For example, if you’re building a house, the critical path might include activities like laying the foundations, building the walls, and installing the roof. All of these are needed to build a house and if any of these activities fall behind schedule, the entire project will be delayed.

What is the critical path method in project management?

The critical path method (CPM) is a tool used to plan and schedule complicated projects. It is based on identifying the critical path of a project and analyzing it to find the minimum completion time for the project.

The method considers the dependencies between different activities and the amount of time required to complete each activity. By understanding the critical path and the amount of “float” or “slack” time available in the schedule, project managers can better plan and control their projects.

A brief history of the critical path method

The Critical Path Method was first developed by Morgan R. Walker of DuPont and James E. Kelley Jr. of Remington Rand in the late 1950s . They were looking for a way to manage the complicated construction projects they were undertaking, so developed the CPM as a tool to help with this.

The method quickly gained popularity and was soon adopted by many companies and industries. Today, the CPM is widely used in project management and is considered an essential tool for planning and scheduling complicated projects.

Key terms associated with the critical path method

• Earliest start time (EST) : the earliest time an activity can start, taking into account the preceding activities and their durations
• Latest start time (LST) : the latest time an activity can start without delaying the project
• Earliest finish time (EFT) : the earliest time an activity can be completed, taking into account the preceding activities and their durations
• Latest finish time (LFT) : the latest time an activity can be completed without delaying the project
• Float or slack : the amount of time that an activity can be delayed without delaying the project
• Critical path : the sequence of activities that determines the minimum completion time for the project

How to find the critical path of a project

You can find the critical path of a project by following these steps:

• List all of the activities in the project, including their durations and dependencies
• Draw a network diagram to represent the dependencies between the activities
• Determine the earliest start time (EST) and earliest finish time (EFT) for each activity by working forwards through the network diagram
• Determine the latest start time (LST) and latest finish time (LFT) for each activity by working backward through the network diagram
• Identify the activities that have zero float (LST = EST) or negative float (LST < EST). These activities are on the critical path

When to use the critical path method

The critical path method (CPM) is an effective tool for planning and scheduling complicated projects. It is best for when the project has a large number of activities, many of which are interdependent. It’s useful when there are a lot of dependencies between different tasks and activities that must be taken into account to schedule the project effectively.

The method can also be useful when there is a desire to accurately predict the completion date for the project, or if resources need to be allocated optimally.

The CPM is generally less effective for simple projects with only a few activities, or projects where the activities are not closely dependent on each other. The method is also not a good fit for projects that have low predictability and require flexibility since the critical path is based on predetermined dependencies and durations.

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The critical path method for product managers

So, if your product development is operating in a project set up and has a high number of dependencies, this tool could be useful for you and your team to better understand your dependencies and the relationship between them.

Also, while many plans are incorrect the moment you finish them, the act of planning can be useful — more useful than the plan itself. Planning gives you space to think about all the factors that will go into your successful product feature or launch and fosters communication between interested parties.

However, CPM is not suitable where there is low predictability or if flexibility is necessary. I have yet to come across a team developing software that can accurately predict how long even the smallest task takes, or that doesn’t have to deal with changing requirements. I believe most product teams operate in a complex environment, over a complicated environment where the CPM is most effective.

The Cynefin framework gives us a way of identifying the structures we operate in and identifies five domains. It covers two of the domains I reference above — the complicated and the complex.

In the complicated domain, things are more predictable and known. You can rely on best practices. Perhaps, if you are developing a product at the later end of the product lifecycle your team is in a complicated domain. However, the complex domain is novel and experimentation is necessary to work out what will be successful. If you are developing anything new you are more likely to fit into this domain and find CPM ineffective.

The critical path method (CPM) is a tool to plan and schedule complicated projects. It is based on identifying the critical path of a project and analyzing it to find the minimum completion time for the project.

For product managers, the analysis of what makes the critical path and consequential planning can be very helpful to foster communication and bring about a shared understanding of the activities needed for success.

However, as many teams operate in a complex, uncertain environment that requires flexibility, the CPM is unlikely to provide the answer you are probably looking for — when will it be done.

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What is the critical path method?

table of contents

Introduction to the critical path method (cpm).

In project management, staying on top of timelines and tasks can be as complex as untangling a ball of yarn. Thankfully, there's a trusted technique to help us out: the Critical Path Method (CPM). This proven approach optimizes planning , streamlines workflow, and helps coordinate a project's diverse components. Buckle up as we take you on a deep dive into the Critical Path Method.

Understanding the Critical Path Method

Definition of critical path method.

The Critical Path Method, or CPM, is a project modeling technique that helps project managers plan, schedule, and execute their projects effectively. It pinpoints the crucial tasks — the ones that, if delayed, would push back the project's entire timeline.

Historical background and development of CPM

Born out of the need to streamline complex projects during the 1950s, CPM was first employed by DuPont Corporation and Remington Rand Univac for plant maintenance and construction projects. This method proved invaluable for managing multifaceted projects with interdependent activities, and it's been a staple in project management ever since.

Essential components of CPM

At its core, CPM operates using three essential elements: tasks, durations, and dependencies. Tasks are the individual activities necessary to complete the project. Durations are the time required to complete each task. And dependencies describe the sequential relationships between tasks.

Explanation of terms related to CPM

For a deeper grasp of CPM, let's delve into its key terms. 'Float' or 'slack' is how long you can delay a task without waiting for the project. 'Early start' and 'early finish' times are the earliest times a task can begin or end without delaying the project, and 'late start' and 'late finish' times are the latest they can start or end without causing delays.

Working of the Critical Path Method

Explanation of the step-by-step process of cpm.

The essence of CPM is in its systematic approach, which is outlined in these steps:

Breaking down the project into tasks: This process, also known as Work Breakdown Structure (WBS) , is crucial in understanding the task hierarchy and organization. Each task should be manageable and distinct with clear boundaries.

Establishing dependencies between tasks: Not all tasks are created equal. Some cannot begin until others are completed - these are known as dependent or sequential tasks. Conversely, some tasks can be undertaken simultaneously - these are parallel or concurrent tasks. This step demands a comprehensive understanding of task interrelationships.

Estimating task duration: An essential aspect of CPM is accurately estimating how long each task will take. This relies heavily on experience, historical data, and sometimes educated guesses. It's wise to factor in some buffer time for unexpected delays.

Creating the network diagram: This visual representation of tasks and their dependencies allows project managers to see the flow of activities and the critical path. This diagram can take the form of a Gantt chart or a flowchart. The nodes (representing tasks) are connected by arrows (indicating sequence).

Identifying the critical path: The critical path is the longest-duration path through the network diagram and indicates the shortest time the project can be completed. Any delay in tasks on this path directly impacts the project completion date.

Visual depiction of CPM with sample network diagrams

Network diagrams create a visual narrative of the project flow. The nodes (or circles) in the network diagram represent activities, and arrows depict the sequence of tasks. The path from the start to the end that takes the longest time is the project's critical path. Any changes in these tasks' duration will alter the project's timeline.

Importance of identifying the longest sequence of tasks - The critical path

The critical path is essential for project managers because it indicates the tasks directly impacting the project's duration. Managing these critical tasks efficiently ensures the project stays on track and any potential delays are mitigated promptly.

Application and benefits of the Critical Path Method

Various sectors where cpm is used.

CPM isn't restricted to any particular industry. Its practical applications span various sectors like construction (for scheduling stages of a building project), manufacturing (for managing production steps), software development (to navigate coding, testing, and debugging phases), and event planning (for coordinating many event preparations).

Real-world examples of CPM application

To illustrate CPM's real-world application, consider the Apollo project by NASA. The CPM managed the thousands of interrelated tasks required to land a man on the moon. The Sydney Opera House project used CPM to manage its complex building process in the construction sector.

The impact of CPM on project efficiency

By identifying the longest stretch of dependent activities, CPM helps maintain project efficiency. It minimizes idle resources, ensures time is well-managed, and guarantees all project activities are aligned toward the end goal. It also allows project managers to prioritize resources and tasks, further boosting efficiency.

Benefits of using CPM in project management

CPM enables better control over project timelines, early identification of potential delays, and more efficient resource allocation. It also improves risk management by identifying the most crucial tasks, enabling focused and strategic contingency planning.

Challenges and limitations of the Critical Path Method

Recognizing the inherent uncertainty in task durations.

One significant challenge in CPM is the inherent uncertainty in task duration estimates. These estimates often rely on past data and personal judgment, making them vulnerable to inaccuracies. Real-life problems, unexpected changes, and other uncertainties can alter task durations, affecting the critical path.

Challenges related to resource allocation

While CPM is excellent for time management, it does not inherently consider resource allocation. Projects often have limited resources, and multiple critical tasks may require the same resources simultaneously. Project managers often need to adjust schedules or resources to manage such conflicts.

Complexity and time involved in creating and updating the CPM

Creating and updating a CPM diagram can be complex, especially for larger projects with many interrelated tasks. Keeping the diagram updated requires consistent effort, making it a time-consuming process.

Limitations of CPM

CPM assumes that the project environment and task durations are stable, which may not always be true. Other methods, like the Program Evaluation and Review Technique (PERT), might be more suitable for highly uncertain or agile environments.

Comparative Analysis: Critical Path Method and other Project Management Techniques

A. Comparison with the Program Evaluation and Review Technique (PERT)

While both CPM and PERT help manage complex projects, they handle task duration differently. PERT uses three-time estimates (optimistic, most likely, and pessimistic) to account for uncertainty, making it ideal for projects where task duration variability is high.

B. Comparison with the Gantt Chart method

Gantt charts provide a visual representation of the project schedule and are excellent for tracking project progress. However, they don't easily show task dependencies and the critical path, making them less suitable for managing task sequences in complex projects.

C. Criteria to decide which project management tool to use

The choice between CPM, PERT, Gantt, or any other project management tool depends on the nature of your project. For deterministic, well-structured projects, CPM works well. For projects with high uncertainty in task duration, PERT could be more suitable. Gantt charts, on the other hand, are great for presenting project schedules and progress to stakeholders. It's also essential to consider the team's familiarity and comfort with the chosen tool.

Using a Critical Path Method Tool is an indispensable part of a project manager's toolkit, providing a roadmap to keep projects on track. While it has limitations and may not suit every project, its benefits in planning, coordination, and efficiency are undeniable. Mastering techniques like CPM will help navigate the complex landscapes of today's project worlds as project management continues to evolve.

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Critical Path Method in Project Management (Examples & How-To)

Last updated on 30th June 2023

In this article we’re going to take a look at the Critical Path Method and answer the question: What is a critical path in project management?

Project management is the future. According to Harvard Business Review , by 2027 around 88 million people worldwide are likely to be working in project management, and the value of project-oriented economic activity will have reached $20 trillion. 

Research also shows that the majority of projects – around 65% – are unsuccessful . In other words, most projects fail and a lot of time and money is wasted. 

To avoid this failure, project managers need to manage projects effectively. And that’s where the critical path method comes in. 

So, let’s get into it…

Article Contents

What is the critical path method? A definition

The Critical Path Method (also known as CPM) is a project management technique that helps you manage your project efficiently by calculating the shortest route to entire project completion. 

The idea is that you identify all of the tasks required to complete your whole project, and then map out your tasks so that you can schedule your project in the most productive way and get an accurate project timeline. 

The Critical Path Method is ideal for complex projects that have a lot of moving parts. By breaking a big project into smaller, more manageable tasks project managers can gain a better understanding of how to get from point A – Z in the most efficient way. 

The history of the critical path method

Critical path finds its origins in the 1950s at the DuPont company . DuPont is a multinational chemical company, and has been involved in everything from developing Teflon to even playing a major role in the Manhattan Project.  

Two mathematicians (James Kelley and Morgan Walker) who were working at the DuPont company in 1957 are credited with developing the critical path algorithm. They were looking for ways to avoid the costs of plant shutdowns and restarts caused by inefficient scheduling. Their research found that if they focused their efforts on performing the right tasks at the right times, they could avoid these issues. And so, CPM was born! 

Prior to this, the company was simply flooding every problem they had with more labour in order to try and stay on schedule. By implementing the brand new critical path method instead, DuPont was able to save 25% on shutdowns .

How to implement critical path in project management

1. define the scope of the project .

The first step towards implementing the critical path method is defining the scope of your project. This means understanding all the tasks that need to be completed in order for you to consider your project a success. 

So, for step one, make a list of all your project tasks. Pretty simple! 

2. Divide your tasks 

Step two involves looking at those tasks in more detail and dividing them up so you can better understand the when, who, and how of the tasks for your project. 

This is important because some tasks will be critical tasks, some will be dependent tasks, and some tasks will be fine to work on in tandem. As a quick example, if you’re making a chicken sandwich then you can toast your bread at the same time as preparing your salad and/or sauce, but you can’t do either of those things unless the chicken is already cooked. So, the remaining tasks are dependent on the first task of cooking the chicken. 

Once you get the hang of it, the critical path method can be used for pretty much everything! 

3. Calculate the shortest route to completion  

Step three – the final step – is about finding your project’s critical path. In other words, scheduling your tasks to calculate the shortest route to completion. CPM is all about efficiency, so if you can work on tasks in parallel then you absolutely should in order to complete the project in the shortest amount of time. 

It can help to assign durations to your tasks here so that you can get a better understanding of how long everything will take. Sticking with the very simple chicken sandwich analogy, this would look something like this:

This is a very simple example of a project’s critical path, but hopefully you get the idea! 

Critical Path Method examples

Now let’s take a look at some more concrete examples of the critical path method in action.  

We’re going to give both a personal and professional example to really look at CPM from all sides and gain the best possible understanding of how to apply it when it comes to managing complex projects.

Planning a family holiday

Planning a family holiday involves a lot of different tasks, some of which can be done in tandem, while others are dependent tasks. 

The first thing you need to do is make a list of the tasks for your whole project. For example: 

• Research different locations
• Find accommodation 
• Book flights
• Book airport transfers
• Buy sunglasses
• Pack suitcase

And anything else you might want to add to the above list! 

The next step is to divide your tasks up, so Mum can be in charge of the location research and booking accommodation, Dad can be in charge of booking flights and airport transfers, and so on. 

This is also where it’s important to identify those tasks that are dependent on one another. So, for example, the airport transfers cannot be booked before the flights or accommodation. But you can shop for sunglasses and pack your suitcase at any time! 

The critical path for this project could look something like this: 

Creating an explainer video

Now for a professional example. We know all about managing explainer video projects because that’s actually how Project.co first came to be! More on that here if you’re interested . 

The tasks required for an explainer video project are: 

• Storyboarding
• Voiceover recording

Again, after listing these tasks the next step is to define and allocate them, and also find out which can be done in tandem. For example, the storyboarding process cannot start without the script. But once the script has been finalised, the voiceover can be recorded in tandem with the storyboard being created. 

If we were to calculate the critical path for an explainer video project it might look a little something like this: 

And that’s that! Why not try following these 3 steps for planning different projects in your life? It’s a great way to get used to the critical path method. 

5 Tips for successful critical path management 

1. use a project management tool .

Implementing the critical path method successfully relies on project managers having the best visibility of all tasks (critical tasks, dependent tasks, basically every single task required throughout the entire project!). Project management software can be very useful here. 

The best project management tools – like Project.co ! – allow you to not only view your tasks in a number of different ways, but allocate them to different team members, add files, notes, priority tags, and so much more. 

Project.co allows you to manage as many different projects as you want with an easy-to-use interface that you can customise to match your branding. You can also invite your clients and stakeholders to collaborate. 

2. Delegate responsibilities

Another key component of CPM is understanding who is responsible for what. This is crucially important if you have multiple tasks being completed in tandem, and it’s also necessary for dependent tasks (as team members need to know when it’s their turn to step in so that they can manage their schedule successfully). 

For project managers, this means delegating these responsibilities and overseeing the schedule to make sure everything is moving smoothly along the critical path. 

Again, project management software can help here because it makes it easy to view your entire team’s tasks at a glance. 

Project.co offers a number of ways to visualise your tasks, including kanban, list view, calendar, or the scheduler view (seen above) which allows you to view multiple team members’ tasks all on one screen.

3. Map out your project visually

Visualising your project will help you to understand how to get from point A to point Z in the quickest way possible, which is what CPM is all about. 

When using the critical path method, one of the best ways to map out your project visually is with a Gantt chart. 

A Gantt chart is essentially a bar chart that illustrates your project schedule. You can see when each task is due, which tasks are dependent on one another, and which can be completed in tandem. 

4. Create predictions

As much as we all wish for every project to sail through with no issues, the likelihood is that something unexpected will pop up. The best way to prepare for this is to make some predictions for what could go wrong and make a plan for what would happen if it did. 

We’d recommend creating a list of assumptions and risks for your project before getting started. It’s also helpful to create a list of resources that you will need so that you have a clear understanding of the scope of your project before getting started. 

5. Assign a project leader 

The critical path method is all about efficiency, which means there’s going to be a lot of moving parts at any given time. It’s important for everyone involved to be focused on their own tasks to ensure that there are no bottlenecks and the project moves forward smoothly. But, additionally, it’s also important for one person to oversee the project to ensure everything stays on track. 

In other words, to successfully implement the critical path method in project management you should assign a project leader whose sole responsibility is making sure that everyone else is managing their tasks. 

Most projects see a couple of hiccups along the way, and it’s the job of the project leader to manage these setbacks as and when they occur so that your project can still be completed as quickly and efficiently as possible.

Final thoughts

Project management techniques like the critical path method help you keep your projects on track so you can complete more projects on time and on budget. 

Interested in finding out about some more project management techniques? Take a look at this next: 10 Best Project Management Techniques for PMs in 2023 . 

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A beginner’s guide to the critical path method in project management

Last updated

21 December 2023

Reviewed by

Mary Mikhail

Large and complex projects require the use of many materials and working parts. Without a clear plan for undertaking such a job, it’s easy to become overwhelmed and skip important tasks. When this happens, your project is less likely to meet critical deadlines. Or it could fail completely.

CPM is used to identify the vital aspects of any project and its dependent factors to define tasks and ensure the project is completed accurately and on time.

Read on to find out exactly what CPM is and how to use it. You’ll also find some examples of successful use cases.

• What is the critical path method?

The critical path method is a project management method used for calculating, planning, and scheduling large or complex projects. It enables project planners and teams to create a clear roadmap of the jobs or activities that are critical to completing a project on time. By identifying and scheduling fundamental tasks, project managers can assign a specific job’s start time, expected duration, and finish time.

Every project contains vital tasks that determine whether it’s completed on time. If any of these tasks fall behind schedule, so does the whole project.

CPM is a step-by-step plan for identifying critical tasks and creating a clear timeline (or path) in which these tasks will be completed. The schedule of these core project steps is the critical path. Once these tasks are scheduled, you can add other (less crucial) activities to the timeline.

What is a critical task?

A critical task is a job or activity central to a project’s timeline. Other activities will also be delayed if these central tasks are not completed on time.

Every project includes core tasks that must be finished before dependent tasks can begin. For example, you can’t put a roof on a home if the frame hasn’t been erected. In essence, critical tasks are the activities that must be carried out as planned to avoid disrupting the project timeline.

Why must non-critical tasks be monitored?

Critical tasks aren’t the only tasks you’ll need to take care of to complete an entire project. You’ll need to carry out other jobs, too. However, these can be executed less urgently. Since they aren’t core steps, you can choose to delay them until they fit into the schedule better.

By monitoring non-critical tasks alongside the undertaking of critical tasks, you can make informed decisions about when each task should be completed. This approach enables teams to complete several tasks simultaneously without critical delays.

Where was CPM first used?

While the US Navy’s Fleet Ballistic Missile (Polaris) Program was running behind schedule, the chemical company DuPont faced delays in plant turnarounds. Those running these projects needed a technique to get them back on track and deliver them as planned.

The developers of the Polaris Program created a solution called the project evaluation and review technique (PERT). DuPont developed the critical path method.

The PERT method calculates three different time estimations to determine the most accurate duration of each task. DuPont’s CPM plan uses a single time duration for the entire task to measure extra costs that would accumulate if the project duration is decreased.

Why is CPM important in project management?

CPM creates a project roadmap that establishes the longest sequence of tasks that must be executed to complete an entire project. By defining core tasks and the tasks that depend on them, project managers can outline the timeframe in which the project can be successfully executed. This helps reduce noise and align priorities, enabling multiple teams to complete tasks simultaneously without delays.

When should you use critical path analysis?

Critical path analysis is a way to refer to the early stages of CPM. CPM typically aims to develop an accurate project schedule, so the process occurs before the project’s start date—perhaps during the project’s planning phase or even during the process of developing a bid or project proposal.

Understanding a project’s critical path can help project managers estimate costs and resources and develop a predictable schedule.

• How to calculate the critical path

Virtually every project is planned based on completing the job as quickly and cost-effectively as possible without compromising quality. This approach offers the best return on investment (ROI) and ensures minimal resource waste. You can use CPM to make informed decisions about the best way to achieve this goal.

To calculate the critical path, start by identifying all tasks in the project. Once you have a clear idea of everything that needs to be done, you can assign levels of urgency based on dependencies and the estimated time needed for each task.

Take these steps to calculate your project’s critical path:

Define all the tasks required to complete the project.

Define the time requirements for each step based on existing knowledge or industry standards.

Establish dependencies (tasks that must be completed before another specific step can begin) for each task.

Identify which activities must be completed on time to avoid delays due to dependencies. These are your critical tasks.

Align critical paths in a sequential timeline with assigned start and finish times.

The significance of float or slack in CPM

Projects are rarely executed exactly as planned. Delays, resource constraints, unexpected incidents, and scope creep create conditions that cause any task to take longer than planned. To prepare for such issues, project managers should consider the consequences of delays.

The time a task can be delayed for without affecting dependent tasks or delaying the overall project is referred to as float or slack .

Activities on the critical path have zero float. If a critical task is delayed, it will immediately affect dependent tasks and the completion of the project. However, many other tasks can have varying levels of float.

High-float tasks can be delayed with minimal consequences. They simply need to be completed before the project deadline or before they affect another non-critical task. Label high-float tasks as low priority so that you focus on assigning resources to critical tasks. When team members become available, they can take care of high-float tasks while other tasks progress simultaneously.

Identifying slack for each task lets you assign start times and juggle tasks without affecting the project’s timespan.

• Planning for unexpected contingencies and constraints

Large and complex projects can take weeks, months, or even years to complete. Long time frames combined with project intricacies may create unexpected changes that force you to expedite some tasks and postpone others.

To take these contingencies in your stride, you’ll need methods in place to address how such issues impact the overall project timeline.

The two most common methods of dealing with contingencies and constraints when using CPM are fast-tracking and crashing.

Fast-tracking

Fast-tracking is easy to understand if you’re used to multi-tasking to stay on schedule. When deadlines are looming, fast-tracking is the process of executing multiple jobs on the critical path simultaneously. This approach requires you to dilute resources to complete multiple jobs at once and can only be used for activities without dependencies.

When you need to meet updated or emergency deadlines, crashing is the process of allocating more resources to speed up activities. You might bring in more professionals or use resources from tasks with high floats.

Crashing is typically used in emergencies because it can impact critical tasks and project scope . When the project scope is affected, you’ll need to inform all project stakeholders .

• Comparing CPM to other methods

CPM isn’t the only project management method for scheduling and prioritizing project tasks. Comparable methods are used to evaluate the duration and dependencies of specific tasks. While these methods have similarities, their overarching goals differ.

Critical path method vs Gantt charts

Gantt charts map out projected activities and track them against a set timeline. Like CPM, they show dependencies between tasks, and you can use them to create a timeline. However, there are distinct differences between the goals of CPM and Gantt charts and how they are displayed.

CPM is displayed as a network diagram, while Gantt charts are displayed as a horizontal bar chart.

Gantt charts show the resources required for each activity.

Gantt charts plot activities on a timescale, while CPM plots them on a network diagram with an estimated time duration for each task.

CPM identifies critical and non-critical paths and calculates project duration. Gantt charts are designed to visualize how project activities are progressing.

Critical path method vs PERT

The project evaluation and review technique was developed around the same time as CPM to solve similar issues, but the techniques are quite different.

CPM and PERT are both used to evaluate project duration. They identify dependencies and provide an estimated duration for each task. However, they have several notable differences in execution.

PERT is used to estimate the time required to complete activities, while CPM is used when task durations are already estimated.

CPM is designed to evaluate time–cost trade-offs and establish priorities, while PERT focuses on meeting deadlines or shortening a project’s duration.

PERT has three estimates for each activity, while CPM only has one.

PERT is often used for projects that have significant uncertainty, while CPM is better suited to projects where tasks are well-defined.

• CPM benefits

The critical path method is an excellent project management tool to help you deliver your project on time and within budget. It can be useful in recognizing potential delays and scope creep while creating a clearly defined schedule for the project.

Below are some of the most common advantages of using CPM for large and complex projects:

Helps prioritize tasks

CPM’s overarching goal is to identify essential tasks and ensure their timely completion.

Identifying the critical path enables you to clarify which tasks depend on one another, establishing the order in which they must be completed.

Once the critical path is defined, you can prioritize the non-critical tasks based on their slack level. The approach eliminates the “noise” in a multi-faceted project and keeps teams on track.

Improves team communication

Large projects typically require the participation of multiple teams with different specialties. These teams work together to establish an accurate critical path. When the resulting CPM diagram is used as a single source of truth, every participant in the project will have similar expectations of how the work schedule will play out.

Optimizes efficiency

CPM is used to identify the earliest possible starting point and the latest acceptable finishing point for each project task.

Mapping out a schedule with accurate timeframes and dependencies can enable project managers to identify areas that could shorten the critical path. You might achieve this by assigning more people to the job or juggling non-critical tasks for optimal efficiency.

Helps create accurate schedules when paired with PERT

PERT and CPM have distinct differences that naturally complement each other. While both techniques are designed to evaluate time, PERT is focused on time management, while CPM addresses how the project timeline affects the budget.

PERT charts contain three estimates for each task, making it easier to discover potential risks and avoid delays.

Helps map out project plans when paired with Gantt

Gantt charts plot project tasks on a time schedule in a horizontal graph, which acts as a visual communication tool. They can be used to track actual progress against planned progress to help maintain an accurate schedule.

When combined with CPM, Gantt charts give you a more detailed view of the product path, including the required resources for each task.

• How to use the critical path method

Now that you have a clear understanding of the CPM’s purpose, you can apply the process to devise an accurate project schedule. Follow the steps below to plan your project using the critical path method:

1. List project activities

Begin by evaluating your complete project and breaking down the necessary work into manageable steps. Create an ordered list of all the tasks required to complete the job.

2. Identify task dependencies

Some tasks can’t begin until others are finished. Examine your list of tasks and define each activity’s immediate predecessor. Some tasks won’t have dependencies, but critical tasks often do.

3. Create a critical path diagram

Identifying dependencies enables you to create a sequence of events. Create a chart that maps out the tasks in the order they should be completed. The network diagram should include arrows or symbols to identify dependencies.

4. Estimate the timeline for each activity

Estimate the time required to complete each task on the diagram using prior experience or industry knowledge.

Use the PERT method to accurately calculate the best-case estimate, the most likely estimate, and the worst-case estimate. These three values can be used to determine slack more accurately and develop a precise timeline.

5. Use the critical path formula

Once you’ve established estimated durations for each task, you can develop a timeline for the entire project using the critical path algorithm. The critical path formula uses a forward pass and a backward pass to establish a timeline.

The forward pass uses a specified start date as the earliest start (ES) for the first task and calculates the earliest finish (EF) by adding the estimated duration. The process proceeds through the schedule by defining the ES as the highest EF of immediate predecessors.

The backward pass calculates late start (LS) and late finish (LF) dates using the lowest LS value from immediate successors to calculate LF. This pass starts with the last scheduled activity and moves backward through the schedule.

Here’s a simple example using a forward pass and backward pass to establish a timeline for a project with three activities: A, B, and C. The numbers represent the duration of each activity in days. Each activity is dependent on the one before it—B is dependent on A, and C is dependent on B.

Here are the activity durations:

Activity A: 3 days

Activity B: 2 days

Activity C: 4 days

Forward pass

Start at the beginning. Set the ES for the first activity to 0.

Activity A:

Duration = 3

EF = ES + Duration = 3

Activity B:

ES = EF of A = 3

Duration = 2

EF = ES + Duration = 5

Activity C:

ES = EF of B = 5

Duration = 4

EF = ES + Duration = 9

The EF of C is the project duration in this case.

Backward pass

Start at the end. The project duration is the LF of the last activity.

LF = EF of C = 9

LS = LF - Duration = 5

LF = LS of C = 5

LS = LF - Duration = 3

LF = LS of B = 3

LS = LF - Duration = 0

You now have the ES, EF, LS, and LF for each activity.

Critical path

The critical path is the path with zero slack (total float). Activities on the critical path have the same ES as LS and the same EF as LF.

In this example, the critical path is A -> B -> C. The project duration is nine days, and any delay in activities on this path will directly affect the project completion date. Activities A and C are “critical” in the sense that they must be completed on time to avoid delaying the project.

6. Identify the critical path

Define critical tasks as those with no slack level (zero float) and align these tasks into a schedule based on immediate dependencies. Assign a time duration to each critical task derived from the formula used in the previous step. The activity sequence with the longest duration is the critical path.

7. Revise during execution

While the critical path is determined during the planning phase, it shouldn’t be set in stone. Update the critical path chart or diagram as you execute the project. As changes occur in the project schedule, you can define ways to address delays. You can develop a more accurate schedule by updating it to account for constraints and contingencies.

• Examples of the critical path method

The critical path method can be used to manage nearly any type of project in which you can estimate the duration time of specific tasks. Observing examples of CPM in practice can help you clearly visualize how the technique is used.

CPM in construction

Building a house is one of the most common examples used to clearly illustrate project planning with dependencies and potential time constraints. Construction is a complex project with many dependencies.

Conduct excavation

Build a foundation

Construct a wooden frame

Lay brickwork

Box in the walls

Build the roof

Wire electricity

Install plumbing

Install heating and ventilation

Lay flooring

Finish wall carpentry

Fasten gutters and downspouts

Install plumbing fixtures

Finish interior carpentry

Put gutters and downspouts in place

Identifying dependencies

Construction involves many dependencies.

The core jobs will outline your project’s critical path. The process of pouring footers and building a foundation is dependent on the starting task—excavation. Similarly, framing is a critical task that must be completed before walls can be constructed and the roof can be built. However, the brickwork and the electricity can be reasonably postponed until a convenient time.

Jobs with float can be executed in parallel to dependent tasks. For example, an available worker can lay brickwork while others are building the roof.

Therefore, jobs on the critical path are most likely to be excavation, foundation, framing, roof, rough wiring, and rough plumbing. The other tasks in the project will have some float and can run parallel to other tasks.

CPM for shorter tasks

It sometimes helps to consider how project management works from a simpler perspective. If you’re a practiced cook, you’re accustomed to the process of taking care of multiple tasks while being mindful of dependencies. Yet, an inexperienced cook could forget essential steps.

Imagine preparing breakfast for friends. You plan to cook pancakes, eggs, and bacon. You’ll prepare many of these foods in tandem, but some steps have dependencies.

Purchase eggs, bacon, flour, milk, maple syrup, oil, and butter

Preheat the oven to 200 degrees to keep the food warm until serving time

Measure and mix the flour, eggs, oil, and milk to create pancake batter

Fry the bacon

Cook the pancakes

Season the eggs

Fry the eggs

Keep the pancakes warm in the oven while you cook the other foods

Top the pancakes with maple syrup

Again, your starting step for this project is a critical task that must be completed before any other activities can begin: purchasing the ingredients.

Moving forward, you can’t cook the pancakes before mixing the batter. However, since you plan to keep food warm in your preheated oven, you can fry the bacon while you’re mixing the batter or flipping the pancakes. Ideally, you would prepare the eggs last so they will be at the optimal temperature when the meal is served.

The jobs on the critical path are most likely to include buying ingredients, preheating the oven, mixing the batter, and frying the eggs. Other tasks can be completed in parallel to these essential steps.

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Critical path method (cpm) : definition for project management.

The critical path method (CPM) or critical path analysis (CPA) is a project management technique used to plan, schedule, and execute complex projects. It involves identifying the essential tasks and their dependencies and calculating their durations to determine the most extended sequence of tasks (the critical path).

Learn more about the project management life cycle:

In this article...

What is the critical path in project management?

The critical path in project management is the sequence of stages determining the minimum time needed for project completion. Any delay in this path directly extends the project’s finish date, making it vital to monitor and manage.

By identifying the critical path, project managers can focus on essential tasks and allocate resources accordingly. This helps to ensure that the project stays on schedule and within budget.

CPM is a valuable tool for project managers working on complex projects with multiple interdependent activities. It is handy for projects where timing is critical and delays in specific tasks could postpone the entire project. 

What are the 3 main objectives of the critical path method?

1. determining the minimum time for project completion.

CPM helps identify the shortest time to complete a project by calculating the minimum time required to finish all the necessary tasks without delay. 

2. Determining the sequence of activities

CPM also helps identify the actions that must be completed on time to ensure the project is finished within the scheduled timeframe. Non-critical paths have some slack time, which means they can be delayed without delaying the project as a whole. 

3. Tracking project progress and taking corrective action

CPM can be used to track the project’s progress concerning the agreed timeline. If the project is delayed, proactive corrective actions can be taken. Techniques such as crashing (applying more resources to the critical path) or fast-tracking (doing tasks in parallel) can compress the critical path and meet the required deadline.

How to use CPM 

1. Identify all tasks: List all the tasks required to complete the project.

2. Determine dependencies: Identify the relationships between tasks, specifying which tasks must be completed before others can begin.

3. Estimate task durations: Assign an estimated duration to each task, considering the time required to complete it.

4. Create a network diagram: Using the tasks, dependencies, and durations, construct a network diagram such as a Gantt chart or a PERT chart.

5. Find the critical path: Identify the longest path through the network diagram. This path represents the shortest time the project can be completed and is known as the critical path.

6. Allocate resources: Focus resources on the critical tasks, ensuring they are completed on time.

7. Monitor and adjust: Regularly review the project’s progress, paying close attention to the tasks on the critical path. Make the necessary adjustments to keep the project on track.

8. Utilize PM software: Consider using project management software that supports CPM, such as Asana or Smartsheet, to automate and simplify the process.

How is the critical path method different from other PM methods?

While understanding its objectives is important in understanding CPM, it’s also essential to understand how the critical path method in project management distinguishes itself from other project management methodologies.

• Focus on time management
• Use of dependencies
• Flexibility and adaptability
• Complexity and suitability
• Integration with other methods

CPM: Focuses on identifying the longest path in the project with the least scheduling flexibility. This helps in determining the shortest time to complete the project.

Others: Other methodologies might focus on different aspects like cost, quality, or stakeholder engagement, not necessarily prioritizing time management.

CPM: Emphasizes the dependencies between tasks and uses them to determine the critical path. Any delay in a task on the critical path directly impacts the project’s completion date.

Others: Methods like Agile or Scrum may not emphasize dependencies between tasks, focusing more on flexibility, collaboration, and iterative progress.

CPM: Generally more rigid and best suited for projects with well-defined tasks and timelines.

Others: Methodologies like Agile are designed for projects where requirements may change frequently, offering more flexibility.

CPM: Often used in construction, manufacturing, or other projects where sequential tasks are interdependent.

Others: Different methodologies suit different types of projects. For example, Agile is often used in software development, where requirements may change frequently.

CPM: Can be used with other methodologies like PERT (Program Evaluation Review Technique) for risk analysis.

Others: Some methodologies are stand-alone, while others can be integrated or customized based on project needs.

CPM is distinct in its focus on time management and task dependencies, making it suitable for projects with well-defined tasks and timelines. Other methodologies might prioritize different aspects of project management, offering various levels of flexibility, resource optimization, and risk management. The choice between CPM and other methods would depend on the specific needs and nature of the project.

What are the benefits of using the critical path method?

Enhanced project oversight.

CPM clearly represents the project timeline, dependencies, and critical tasks. This allows for better understanding and control over the project’s progress, helping to identify potential bottlenecks and areas that need attention.

Optimized resource allocation

By identifying the critical path, project managers can allocate resources more efficiently to the tasks that impact the project’s completion date the most. This ensures that essential tasks are prioritized, reducing the risk of delays.

Flexibility in managing non-critical tasks

CPM highlights the critical tasks and identifies the slack or float in non-critical tasks. This information allows project managers to have flexibility in scheduling these tasks, providing a buffer that can be used to accommodate changes or unexpected issues without affecting the overall project timeline.

What are the drawbacks of using the critical path method?

Complexity in large projects.

Creating and maintaining the critical path can become complex and time-consuming for projects with many tasks and dependencies. This complexity might lead to errors or oversights if not managed carefully.

Dependence on accurate estimates

CPM relies heavily on accurate time estimates for each task. If these estimates are off, it can lead to incorrect identification of the critical path, potentially causing delays and misallocation of resources.

Potential ignorance of non-critical tasks

While focusing on the critical path is essential, there’s a risk of neglecting non-critical tasks. If these are not managed properly, they can become critical and affect the project’s success.

How can project management software support the critical path method?

Project management software simplifies the critical path method by automating the process of identifying tasks, dependencies, and durations. It provides visual representations like Gantt charts, enabling real-time critical path tracking. This helps with quick adjustments and resource allocation and ensures the project stays on schedule. 

When selecting project management software for critical path analysis, consider the specific needs of your project. Look for features like task scheduling, dependency tracking, and resource management. Evaluate the software’s ease of use, scalability, integration capabilities, and customer support to find the best fit for your project. 

Asana allows users to create and organize tasks, define dependencies, and visualize the project timeline, including the critical path. Real-time collaboration, resource allocation, and integration with other tools enhance the process, while customizable dashboards enable close monitoring of critical tasks. Asana’s flexibility and user-friendly interface make it a valuable asset for managing the critical path, ensuring timely project completion and optimal resource utilization.

Wrike is a PM tool that supports the CPM through features like Gantt charts, which allow for clear visualization of task dependencies and the critical path itself. The platform’s real-time collaboration capabilities enable seamless communication among team members, ensuring alignment on critical tasks. Wrike’s flexibility in resource management and scheduling aids in the precise allocation of resources to critical tasks, while its reporting and monitoring tools provide insights into the project’s progress.

Smartsheet is a PM tool that facilitates the implementation of the CPM through its interactive Gantt charts and dependency tracking. These features allow project managers to visualize and manage the critical path, identifying the tasks that must be prioritized. Smartsheet’s resource management capabilities ensure that essential tasks have the necessary resources, while its real-time collaboration and reporting tools provide continuous insights into the project’s status.

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Mastering the Critical Path Method: A Comprehensive Guide

Learn how to manage your projects using the critical path method effectively. Our guide provides detailed step-by-step instructions for your benefit.

For a project to succeed, it has accomplish its business goal and also meet two other requirements. It needs to be completed on time and within budget. Those seem reasonable enough, particularly in the context of a business venture, when time and money are precious. Yet, according to the  Project Management Institute , nearly half of projects fail to meet those simple standards.

The critical path method (CPM) was one of the first tools developed in the discipline of project management. Despite its relative age, using the CPM can make the difference between planning a successful project and setting unmeetable deadlines.

In this article, we’ll explain the critical path method in simple terms. We’ll also discuss how to use it in your own projects, so you always successfully meet your deadlines.

What is the critical path method?

The definition of the critical path method may seem counterintuitive at first glance. It identifies the ‘path’ in a project, or linked set of dependent tasks, that takes the longest to complete.

Here’s a sample building project with the critical path shown as red arrows. By determining this path, you can calculate the minimum length of time the entire project will take. Let's break down each part to understand that more clearly.

A project task or activity is fairly straightforward to understand. It's one step in a multi-step project. A classic example of working with the CPM is building a house. One task in house building might translate to laying a foundation, stringing electrical wire, or making the frame.

A dependent task can only be started once another task is completed. In our house-building example, you can only build a frame once the foundation has been laid. Therefore, framing the building  depends  on the foundation being completed. There are other types of dependencies, but this is the most common.

You can link dependent tasks together in order. For example, house building might include a path between laying the foundation, putting up the framing, adding the wiring, and so forth until the house is complete.

Most projects have multiple paths that diverge and converge. Nearly every task in house building depends on laying the foundation, but plumbing and wiring don't necessarily depend on each other. Therefore, each has a separate path.

Critical Path

Some paths take longer to complete than others. The 'longest' path is the one that takes the most time to complete. This is the  critical path  as it determines the minimum time required for the overall project.

Returning to our house-building example, all the landscaping tasks, or the landscaping path, may be completed fairly quickly. However, the much more time-consuming path of laying the foundation, framing, drywalling, and roofing determines how long the project will require.

Knowing how long it'll take to complete the landscaping is helpful. However, understanding the much longer critical path allows you to determine time requirements for the entire project schedule. Complex projects may have multiple critical paths. In addition, the critical path may change as tasks are adjusted, removed, or added.

Why is the CPM important to project management?

The critical path method's primary use is in scheduling. Not only will it allow you to determine the minimum time needed to complete the project, but it also allows you to schedule individual tasks. It also clarifies dependent relationships, so you know what else you must complete before starting each task.

The critical path method identifies the critical tasks to meet your deadlines. The tasks that aren't on the critical path have more flexibility. CPM, therefore, reveals where to focus your efforts, to reduce the overall project time requirements. Each aspect can improve your chances of  completing a project successfully .

Note that 'method' in this case predates the idea of project management methodologies. CPM is a tool that can be used within many project management methodologies but doesn't make up a whole PM methodology itself.

Important terms for the CPM

There isn’t a lot of technical jargon to learn to apply the critical path method. However, understanding a few key terms will make using the critical path method much easier.

• Earliest start time  - The earliest you can start each task. This may be affected by deadlines for previous tasks in a path.
• Late start  - The latest a task can begin without delaying the overall project. It's also possible to use a critical path analysis to work backward. Doing this establishes the latest a project can start and still be completed on time.
• Earliest finish time  - The earliest a task might be finished, considering estimated time requirements and those of previous tasks it depends on.
• Late finish  - The latest a task might be completed without delaying the overall project.
• Float  - Broadly, the difference between the early and late start and finish times. In other words, how long a task can be delayed without delaying the project. There are two types, free float, and total float.

How to find the critical path

Many apps out there'll help you determine the critical path, particularly for complex projects with many tasks. However, it's important to understand how the critical path is found, so you can make sure the software is doing its job correctly. For small projects, doing it by hand may also be helpful.

List activities

Before you can begin, you need to know all the tasks required to complete your project. The list of tasks is often laid out in the work breakdown structure (WBS), another classic project management technique. This requirement can limit CPM's usefulness because not all project management methodologies can provide a complete list.

Identify dependencies

Before identifying a critical path, you must understand how each task depends on others. Do the two tasks of adding wiring and plumbing actually depend on each other? To use the CPM successfully, you have to know enough to create paths that accurately represent the project.

Create a network diagram

In simple terms, create a flow chart that maps out each path and all the dependencies. More technically, critical path diagrams are usually activity-on-node network diagrams. These diagrams use squares, or nodes, connected by arrows to show a logical sequence of tasks. These graphs provide an easy way to show dependent paths, so it's possible to spot the critical path.

The simplest forms of activity-on-node graphs are easy and intuitive to use. Detailed versions provide different ways of representing different types of precedence relationships.

Estimate task duration

Estimate the time requirements for each task. CPM doesn't offer a method for making those estimates, so you may need to try another tool, like the project evaluation review technique (PERT). You can also investigate more refined techniques that measure effort rather than simple duration. Project management software exists that can also help you make time estimates.

More sophisticated methods estimate time requirements using effort and resource calculations. In other words, they consider each task's expected work hours and the number of workers assigned. It’s a method that is more accurate, and it is often software-assisted.

Calculate the critical path

Once you have the diagram and time requirements for each task, you can identify the critical path and estimate the total time for the project. The total of the durations of tasks on the critical path determines the shortest time required for the project. You can also add information like early and late start times or early and late finish times.

Advantages and drawbacks of the critical path method

The critical path method is a vital tool for most projects. It offers a range of advantages, though it also has some drawbacks.

• Determine the longest path to estimate project duration
• Helpful in planning a project and staying organized
• Clarifies task dependencies so you can avoid bottlenecks
• Identifies the critical tasks, allowing you to focus resources
• Creates a realistic timetable for the project
• Using CPM can be time-consuming
• Resource requirements must be considered for accurate durations
• Complex projects may have more than one critical path

CPM vs. PERT

Early project managers developed PERT around the same time as CPM. The two methods have some similarities. In particular, they are both concerned with the duration of tasks in a project.

However, the purpose of the two techniques is different. The critical path method assumes you already have time requirements for tasks. On the other hand, PERT is a method of estimating the time requirements of a task.

Moreover, CPM considers only one value for time requirements. PERT provides three estimates, one each for the best, average, and worst-case scenarios.

Critical path examples

Explain a simple example of a critical path analysis for a basic 'project,' cooking a steak dinner. Creating a critical path ensures your steak doesn't sit and get cold while waiting for your side dishes.

1. List activities  - Begin by listing out each activity and its time requirements. For our example, we'll use a short list of representative tasks. a. gather ingredients, b. chop vegetables, c. preheat the oven, d. prepare meat, e. roast vegetables, f. cook meat, g. and serve.

2. Identify dependencies - 'Gather ingredients' has to come first. Then, two paths separate. In one, the oven is preheated, and the vegetables are chopped and then roasted. In the other, the meat is prepared and then cooked. The two join for the final task, serving the food.

3. Create a network diagram  - A simple diagram is enough for this example.

4. Estimate task duration - Come up with some estimated numbers using a variety of methods. For our tasks, estimates work out to be: a. gather ingredients - 5 min, b. chop vegetables - 10 mins, c. preheat oven - 5 min, d. prepare meat - 5 min, e. roast vegetables - 20 min, f. cook meat - 10 min, g. serve - 2 min.

5. Calculate the critical path  - In our example, the ‘roasting vegetable’ path takes 37 minutes. The path for cooking the steak took only 22 minutes. Roasting the vegetables is the critical path in this case.

A well-done critical path analysis can help you successfully make a delicious dinner with everything getting done in time to serve together. While the steak is the highlight, preparing and roasting the vegetables takes the longest. As a result, the 'roasting vegetables' path determines the shortest time required to project completion.

CPM in waterfall project management

The critical path method is one of the first truly modern tools used in  waterfall project management . It might be considered a proof of concept that project management was a separate discipline rather than just a skill that the chief engineer or project administrator should cultivate.

In that sense, CPM helped define waterfall methodologies and works well with a waterfall project management style. Many projects that still predominantly use waterfall methods, like construction, often depend on CPM and similar tools.

CPM in Agile project management

Many classic PM tools from the age of waterfall management can still be useful when an  Agile PM methodology  is used. However, the critical path method may not be one of them. The CPM depends on a clearly defined list of known requirements and tasks, which Agile projects usually can't provide.

Using iterative work processes, which feature heavily in Agile methods, will also make it difficult to use the CPM. The project team returns to the iterative tasks an unknown number of times, so estimating the total time is difficult.

Use the CPM in your critical projects

In some ways, the development of the critical path method marks the beginning of modern project management. It remains a crucial tool for ensuring a project's success almost a century later. It allows you to set realistic deadlines and helps focus your efforts where they'll do the most good.

Using Motion  can help you match a theoretical CPM-determined schedule with your real-life availability and set the most critical tasks to high priority. Motion also allows you to share with teammates, get their input, and complete work on time.

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What Is the Critical Path Method in Project Management?

Laurenzo Overee - Guest Contributor

What is the critical path method?

Why use the critical path method, how to find the critical path of a project, critical path analysis example, optimize the critical path method for your projects, are you constantly struggling with multiple task timelines applying the critical path method can help put things into a clear perspective..

The critical path method (CPM), also known as critical path analysis, is a simple but effective project management technique. Users can apply CPM in analyzing, planning, and scheduling the most complex projects and may combine it with program evaluation and review techniques for optimal results.

CPM identifies the necessary tasks required for completing a project. The project management technique determines scheduling flexibilities to help teams handle task efficiencies while managing realistic time frames for their projects.

A collaboration between DuPont and Remington Rand UNIVAC saw the development of the CPM technique in the 1950s [ 1 ] as a solution for reducing the cost of inefficient scheduling practices.

A CPM approach usually involves the breakdown of relevant project activities, activity duration, and the relationship and dependency between tasks and logical endpoints such as project milestones.

/ Benefits of a critical path analysis

A critical path analysis enables your team to assess and analyze project activities while promoting resource management.

For instance, CPM helps teams communicate project plans and schedules, driving improved cost management and performance. Task segregation (into critical and noncritical groups) can help you prevent project bottlenecks by running certain activities concurrently.

Also, CPM presents a practical and organized base that effectively guides teams toward fulfilling project objectives with reliability. Your team may apply CPM as an accurate benchmark for future projects based on real-world expectations and observations.

/ What is a critical task?

Essentially, you may consider the critical path the longest possible sequence of activities that teams must finish on schedule to complete a project. As such, the slightest delay observed in each stage of your CPM will push back the completion of the entire project.

Ultimately, using the CPM helps teams prioritize and manage multiple contingencies and necessary fixes to keep your most complex projects running smoothly according to schedule. The CPM works well, especially during peak periods when teams juggle several projects that compete for their limited time, resource, and attention.

Essentially, your project managers and stakeholders may apply the CPM to manage expectations and realistic deadlines from the beginning of your project.

You can define the critical path of a project through a meticulous process that identifies the correlation between project activities and puts your tasks into a clearer perspective.

Although modern automated software solutions can help your team figure out the critical path of your project through algorithms, you can choose to perform a manual calculation instead for a greater understanding of your project flow.

List all project activities

A complete specified listing of your project activities provides a bird's-eye view of each task and its correlations. Applying a work breakdown structure can help systematically manage each task dependency associated with your deliverables.

Define the project dependencies

There are four primary types of dependencies in project management. These dependencies include finish-to-start, finish-to-finish, start-to-start, and start-to-finish relationships. A CPM approach requires you to identify every single dependency in every project phase to create a critical path.

Create a critical path network diagram

Modern visual workspaces can help your team create critical path network diagrams that visualize critical path networks through customizable templates for easy reference and management. These network diagrams will present a flowchart that displays how your tasks interrelate.

Estimate task duration/timeline

Your visual workspace tools can also help tabulate task durations and timelines to determine the priority of each task and how they compare with other activities in your project. You can make estimations based on historical project data, industry trends, and conjectures guided by knowledge and expertise.

Calculate the critical path

Once you have fully tabulated project task durations and timelines, you can identify the critical path as the sequence of activities with the lengthiest duration.

Determine floats

The float or slack within a project refers to the degree of flexibility for a specific task. As such, floats inform your team about the workable leeway available without impacting the overall project progress. There are two types of float to consider in your CPM: total and free.

Your CPM’s total float value equals your project’s late start time - early start time or late finish time - early finish time. For free float calculations, you may take the next task - the current task.

The total float determines the allowable time for delaying an activity from the early start date, which does not compromise the project finish date. Similarly, free float refers to the task delay time that does not affect the following tasks.

Revise as needed

Revise your CPM when required since your schedules depend on estimated activity durations. You can compare your original CPM with measured real-time CPM values of your projects for improved assessments of future projects.

A project manager begins the CPM process by considering the number of attributes for each project activity, which determines its duration.

These attributes may include:

Early Start (ES)

Late Start (LS)

Duration (the estimated time for task completion)

Early Finish (EF)

Late Finish (LF)

Float/Slack

While the manager cannot predict every possible attribute, critical path analysis can help identify them.

For instance, if a predecessor task requires 20 days for completion, it inherits the predecessor’s EF as its ES. As you work through your project with CPM, you will observe the correlations [ 2 ] between the LF and EF of activities, establishing the float value that determines the flexibility of your tasks.

CPM-based programs offer visual presentations with timeline views, customizable templates, and collaborative tools that keep multiple projects on track with consistent success. Visit Capterra’s CPM-friendly project management software to help you prioritize your project management without exception.

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Critical Path in Project Management: Definition, Method

The method defines how long it will take to complete a project and what key activities will compose the scope of work… Let’s learn more about this technique, explore the definition of CP, and view example use of network diagram in MS Excel spreadsheet.

What is a Critical Path in Projects?

CPM was developed as a formal project scheduling technique in the United States in the early 1950s. The key focus was placed on managing project finance through reducing task completion times. The method was first applied at industry level to model product development, engineering, construction, aerospace, and other project environments. It was implemented at lower levels (company, department, team) later on.

Since that time, critical path in project management has been modified many time and new definitions and categories have been added. So, today the original definition of critical patch is no more in use, however the fundamentals remain current.

Critical Path Defined

Critical Path (CP ) is defined as the longest estimated sequence of interdependent activities that should be accomplished on time to ensure completion of the project on due-date. The critical path activities are performed under the “predecessor-successor” relationship, so that any next activity cannot be started until its predecessor is complete.

As implied by this definition, CP represents the most important tasks or events that are organized into a dependency sequence and that directly impact the project’s completion date. These tasks/events determine the longest duration for the entire work and are helpful in activity scheduling and resource allocation.

Flexibility Time and Float

CP is the way to minimize risk of failure and understand where the project manager has and doesn’t have flexibility in decision making.

In this context, a flexible decision means that there are some tasks that can be started earlier or later without jeopardizing the completion date, so that the manager can manipulate and adjust the project schedule taking into account the time period between the earliest start date and the latest end date of each activity. That time period is rarely called “ flexibility time ” and rather frequently called “ float ” or “ slack “. By definition, an activity that has float time will not be included in the critical path.

Float is the amount of time for which an activity can be deployed without delaying the completion date of subsequent tasks (successors) or the entire project.

Critical Path Method Definition

Critical Path Method (CPM) defines a scheduling technique intended to predict work duration by using network analysis. The CPM is a set of practices and techniques used rather in complex projects to identify and sequence the activities ( critical path ) that have the highest impact on the project’s due-date, to schedule time required for their completion, and to establish the predecessor-successor relationship between the activities.

The method of critical path in project management involves use of network diagrams to make it easier for decision makers to see how long each activity will take. CPM is essential in predicting work timeline, and through using the method in combination with activity network diagrams the project manager is enabled to:

• Schedule the estimated time (duration) each task or event will consume
• Combine all activities’ durations into a timescale for analysis
• Figure out how each activity impact the progress of the project plan
• Make right team assignments regarding the critical tasks

Activity Network Diagram to Visualize the Critical Path

As said above, one of the best ways to ensure effective project planning and scheduling is to use activity network diagram . Such a diagram makes is easier for planners to visualize possible activity paths and define the critical one.

Teams use network diagrams to get a visual of the entire work broken down into interdependent tasks and to plan their further actions accordingly. Bubbles, boxes and arrows will help understand the activities and how they are link to each other. The project manager produces the diagram to model the activities flow and visualize the critical path definition . Each activity is marked either with a certain code (ID) or name; activity paths need to be highlighted. Below is an example.

This activity network diagram shows three possible paths to do the project from start till completion. The green, yellow and red arrows indicate how the activities need to be sequenced in each respective path

Example: MS Excel Spreadsheet for CP Method

In your work breakdown structure, you have a complete list of all activities to be carried out within your defined project , from start to finish. Your goal is to analyze the duration and predecessor(s) of each activity and then to try to draw a network diagram. Activities that have zero float time and must be completed on time can be added to your critical sequence.

Critical path in project management can be analyzed and visualized with help of spreadsheet software . For example, you can use MS Excel to create a spreadsheet with all of your project tasks in it, including their ID, Duration, Predecessors, and Successors. Alternatively, you can use MS Project that offers greater functionality for defining and analyzing critical paths in projects.

MS Excel lets you create a spreadsheet for analyzing activity sequences by duration to define the critical path which has the longest duration

In this critical path Excel spreadsheet, we have three possible sequences that carry out the project from start to completion. As a project manager, first you need to calculate the overall duration of each sequence and then compare the durations against each other. The activities that define the longest overall duration will compose the critical path (in our example, it is path “C1-C2-C3” with duration “30 days”).

Your next step in analyzing critical path method is to create Gantt Chart to visualizes CP on calendar. Gantt Chart will help you design a project schedule and agree on activity durations and float time. Both MS Project and MS Excel can help you with designing Gantt Chart.

Common Questions and Answers about Critical Path

• What type of chart typically displays the critical path? A critical path is often represented on a Gantt Chart. It starts at the start of activity 1 and extends to the end of activity n. Network diagrams help show interdependent activities
• Can there be more than one critical path? There can only be one critical path in a project schedule — the series of activities with no float time, extending from start to finish.
• How do you decide on the critical path? Once you know your project’s activity list and their durations, you can visualize them in a network diagram. By looking at the diagram, you’ll see which activities are on the critical path and which ones aren’t needed (they’re off the critical path). This will help you plan your project better and get a better handle of its progress.
• Can critical path have float? Once you’ve identified the longest duration for each activity, if its float time is under a week, it can be removed from the critical path and added to your extended float time.
• Can critical path analysis be used for any type of project? The CP method can be used for any project where there are multiple tasks that need to be completed in a certain time frame. It can be used for projects in IT, engineering, construction, marketing and operations.

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The Complete Guide to Critical Path Method (CPM)

October 13, 2023 - Updated on October 13, 2023

The Critical Path Method (CPM) is one of the classic project management methodologies. The journey from the initial idea to project completion involves numerous phases, role distributions, responsibilities, and leadership.

It is precisely in mapping the key segments of the Critical Path Method that its significance comes to the fore because it enables the team to clearly identify the points in the project that largely determine the outcome.

In the following text, we will break down the Critical Path Method into parts and explain each one, giving you a clear understanding of how to reach your desired goal.

Let’s dive in!

What is the Critical Path Method (CPM)

We can say that the project management industry changed for the better when it adopted this methodology that originated in the 1950s as a highly efficient technique for completing projects.

First, let’s cover the Critical Path Method definition.

The Critical Path Method (CPM) primarily entails focusing on key tasks within a project , without which there simply cannot be a positive project outcome. Of course, all tasks assigned to a team need to be completed, but the critical ones are those where there is no room for compromise.

On the other hand, project managers willingly use CPM because it has been empirically proven that they can easily achieve an effective scope of work, which team members naturally follow.

So, the task of a project manager is to identify which activities are crucial and to explain to their team why they need to adhere to that path, highlighting the benefits it brings.

It is crucial for team members to understand that the only way to achieve the goal by using this methodology involves closely monitoring and following the established timeline and adhering to individual deadlines for each task.

Importance of Critical Path Method

CPM allows for a complete insight into project management and the team regarding all project tasks and when and how they should be executed.

Here, we will highlight the three most important reasons why the CPM process is considered a crucial segment of the project management workflow :

• Critical activities . Breaking down the project into smaller tasks and assigning priorities enables the project team to have a clear picture of which tasks are crucial. This will allow them to allocate their creativity and avoid spending their energy and effort on tasks that cannot be categorized as “crucial.”
• Time . Smart allocation of time required for each important task cannot but result in overall team efficiency and, consequently, project schedule efficiency. On the other hand, it will save time that can be used for other secondary activities.
• Cost . If you save time, you will also save money. That is why implementing the Critical Path Method ensures cost savings, especially when it comes to avoiding expenses that can arise from secondary tasks in the project.

When Should You Use the Critical Path Method?

You should use the Critical Path Method for complex projects since this methodology breaks down a project into smaller components or tasks and assigns deadlines for their completion.

Complex projects typically last 2 or 3 years and require the completion of numerous activities within that time frame. They are characteristic in construction, product development, medicine testing , and similar fields.

Let’s consider the construction of a student campus as an example. It involves performing legal tasks related to contracts and permits, executing tasks for the architecture and construction teams, procuring materials, and carrying out various technical works. These tasks represent the project’s key tasks, and each has a specific deadline.

How to Use the Critical Path Method

Once we have defined what it is, its significance, and when to use the critical path method, it remains to clarify the steps involved in this method with some critical path method examples.

This project management technique will help you identify primary and secondary activities, understand the relationships between all activities, and enable you to easily track your activities by determining the time required for each.

#1. Identify the Activities

First and foremost, when faced with a specific project and a defined goal, in order to avoid getting lost and wandering off track, it is necessary to divide your project into stages or activities. Determine all the activities that need to be performed in order to complete the project .

For example, if you are tasked with writing a paper (academic or scientific), initially, you only have a topic. To address the given topic in your paper, you need to cover various areas related to it. This can be achieved by breaking down the given topic into essential segments or components, which will provide you with the framework for what you need to write.

#2. Identify the Dependencies

Once you have listed all the activities required for your project, it is important to determine the relationships or dependencies among these activities. Identifying activity dependencies will further assist in prioritizing them, determining the sequence in which they should be executed, and distinguishing between main and subsidiary activities.

For instance, you need to identify activities that need to be started or finished until another activity is completed or initiated. Additionally, you should identify activities that can be performed in parallel or completed simultaneously.

Recognizing the dependencies among activities is crucial because the completion of the entire project depends on the smooth functioning of each individual activity.

#3. Design a Network Diagram

Network diagrams help you visually understand all the activities involved in a project, along with their dependencies.

By using diagrams, you gain a clear overview of the initial activities, their start times, and expected durations, and as the project progresses, you can visually track the workflow and see how activities are being executed.

This allows you to monitor whether activities are being completed within the scheduled time or if there are any delays.

You can design network diagrams using various techniques and tools . One approach is to create the diagrams yourself, using different symbols and labels.

For example, you can use rectangles to represent upcoming activities and different colors to indicate their relative importance. Arrows can be used to illustrate the connections and dependencies between activities.

There are also software tools available, such as Microsoft Project , that provide templates and features specifically designed for creating network diagrams. These tools make it easier to create and update the diagram as the project progresses, as they often offer built-in functionalities for managing tasks, dependencies, and timelines.

#4. Estimate Activity Duration

A well-executed project requires a good plan, and part of that plan is determining the time required to complete each planned activity. Therefore, it is necessary to estimate the duration of each activity .

This step is crucial because the completion of activities determines the project’s overall timeline, and in order to maintain a smooth workflow, it is important to realistically plan the execution time for each activity.

To estimate activity duration, you can utilize various indicators . These indicators may include theoretical calculations, past experience, and statistical data. By considering these factors, you can arrive at a reasonable estimate of the time required for each activity.

It is important to note that the estimated duration should neither be overly optimistic nor excessively conservative. It should be a realistic average that takes into account potential unforeseen circumstances or delays that may arise during the execution of activities.

#5. Calculate the Critical Path

To calculate the critical path, you need to determine the longest series of interdependent activities that, if not completed on time, would cause project delays .

First, you must calculate the individual durations of all interdependent activities, considering their earliest possible starts and earliest possible completions.

Next, you need to determine the execution of these activities, with their latest possible starts and latest possible completions.

By doing so, you can identify the specific time at which interdependent activities, crucial for project completion, can start or finish at the latest, both individually and in their interdependencies. This analysis is crucial to preventing project delays.

#6. Determine the Floats

Determining the floats helps identify the flexibility in scheduling non-critical activities without impacting the project timeline . Float, also known as “slack,” represents the amount of time an activity can be delayed without delaying the overall project’s completion.

To calculate the float for identified activities, we consider two values: the earliest start time (ES) and the latest start time (LS). The float (F) is then determined when you simply subtract the ES from the LS:

Float (F) = LS – ES

If the float value is zero, it indicates that the activity is critical, and any delay will directly impact the overall project timeline . Conversely, a float value greater than zero signifies that the activity can be delayed without affecting the project’s completion.

Critical Path Method vs. Gantt Chart

The Gantt chart is also a project management tool used for tracking your project, providing you with a visual overview of your activities and how they progress . In a Gantt chart, activities are typically listed on the left side, while you track their execution on the other side.

The chart represents the timeline of these activities, indicating when they start, how long they will take, and when they finish. Within the Gantt chart, various options exist, such as using different symbols to mark important elements like project milestones or activity dependencies.

Additionally, you can use different colors to represent different project phases. All of these features facilitate a clear view of the project’s status.

On the other hand, the Critical Path Method (CPM) provides insight into the overall project duration by considering the individual shortest and longest durations of activities, as well as their interrelationships and dependencies.

The goal is to identify the critical path—the series of steps whose disruption would have the greatest effect on the project’s schedule.

Critical Path Method vs. PERT

Although both techniques aim to achieve results in the shortest possible time, there are some key differences between these two methods.

PERT primarily represents a visual project management method , while CPM is a statistical method.

For projects without precisely defined durations, PERT is more suitable. It allows you to analyze activities and estimate the time required for their completion before the project starts, focusing primarily on organizing activities, planning, coordination, and management.

On the other hand, the critical path method focuses more on executing all the necessary activities within a given timeframe to ensure the successful completion of the project.

The Critical Path Method can make that complex project look much more manageable.

By identifying key activities and allocating the required time for each of these critical points, the project management team can ensure an efficient project schedule.

On the other hand, team members who work on the project on a daily basis will be able to concentrate more easily on what is important, ultimately resulting in a flow that will benefit everyone on the team.

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The Defense Acquisition Encyclopedia

Schedule Development

The Critical Path Method (CPM) is a way to determine the critical path of a schedule. The critical path is the longest path of scheduled activities that must be met to execute a project.  This is important for Program Managers (PM) to know since any problems on the critical path can prevent a project from moving forward and being delayed.   Earned Value Management (EVM) analysis focuses on critical and near-critical paths to identify cost and schedule risks. Unlike the critical path, other schedule paths might have slack time to avoid delaying the entire project. There might be multiple critical paths on a project. The method is used with Program Evaluation and Review Techniques (PERT) .

Definition: The Critical Path Method (CPM) is a scheduling technique to determine a schedules critical path by calculating the longest path of planned activities to the end of the project and the earliest and latest that each activity can start and finish without making the project longer.

Critical Path Method (CPM) Goal

The goal of the Critical Path Method (CPM) is to determine the critical path of a schedule in order to focus resources more efficiently. The method helps Program Managers (PM):

• Understand which tasks are on the critical path to determine a completion date
• How best to manage tasks around the critical path to meet the scheduled end date
• Focus on preventing schedule slips
• Gain insight when planning work packages and tasks

Benefits of Using the Critical Path Method (CPM)

Here are a few good reasons to use the CPM method:

• Improves Planning: CPM helps plan for the future by comparing expected progress to actual progress. The data from current projects can be used to help plan for future projects.
• Helps with resource loading: CPM helps project managers put tasks in order of importance, which gives them a better idea of how and where to use resources.
• Highlights bottlenecks: When projects get stuck, valuable time is lost. Using a network diagram to show project dependencies will help you figure out which tasks can and can’t be done simultaneously so that you can plan your schedule accordingly.

Determining the Critical Path

The Critical Path is determined when analyzing a project’s schedule or network logic diagram and uses the Critical Path Method (CPM).  The CPM provides a graphical view of the project, predicts the time required for the project, and shows which activities are critical to maintaining the schedule.

Critical Path Method (CPM) Development Steps

The seven (7) steps in the CPM are: [1]

• Step 1: List of all activities required to complete the project (see Work Breakdown Structure (WBS) ),
• Step 2: Determine the sequence of activities
• Step 3: Draw a network diagram
• Step 4: Determine the time that each activity will take to completion
• Step 5: Determine the dependencies between the activities
• Step 6: Determine the critical path
• Step 7: Update the network diagram as the project progresses

The CPM calculates the longest path of planned activities to the end of the project and the earliest and latest that each activity can start and finish without making the project longer. This process determines which activities are “critical” (i.e., on the longest path) and which have “total float” (i.e., can be delayed without making the project longer). [1]

Example of Using the Critical Path Method (CPM) to Build a Backyard Deck

The Critical Path Method (CPM) is a technique that allows you to identify tasks that are necessary for project completion and determine the minimum time required to finish the project. It also helps you to manage task dependencies and avoid delays².

To use the CPM for building a backyard deck, you need to follow these steps:

• Step 1: List all the activities or tasks required to complete the project, such as measuring, cutting, assembling, painting, etc.
• Step 2: Estimate the duration of each activity or task, based on the resources available and the complexity of the work.
• Step 3: Identify the dependencies between the activities or tasks, such as which ones need to be done before or after others.
• Step 4: Draw a network diagram that shows the sequence and dependencies of the activities or tasks, using nodes to represent activities and arrows to represent dependencies.
• Step 5: Calculate the earliest start time (ES), earliest finish time (EF), latest start time (LS), and latest finish time (LF) for each activity or task, using the forward and backward pass methods.
• Step 6: Calculate the total float (TF) or slack for each activity or task, which is the difference between the LF and EF or between the LS and ES. The float represents how much activity can be delayed without affecting the project completion time. (See Below)
• Step 7: Identify the critical path, the longest path in the network diagram with zero float. The critical path determines the minimum completion time of the project, and any delay in any activity on this path will delay the entire project.

Here is an example of using the CPM for building a backyard deck:

The table below shows the calculations for ES, EF, LS, LF, and TF for each activity:

The critical path for this example is A-B-D-F-G-H, with a minimum completion time of **20 hours**. Any delay in any of these activities will delay the entire project. The activities C and E have some float, which means they can be delayed without affecting the project completion time.

Calculate Float Time in the Critical Path Method (CPM)

Float time, also known as slack time, is the amount of time that a task can be delayed without affecting the start of the next task or the project completion date³. Float time can be calculated for each task using the following formulas:

• Total float: This is the difference between the latest finish time and the earliest finish time of a task, or between the latest start time and the earliest start time of a task. The formula for total float is TF = LF – EF or $TF = LS – ES where LF is the latest finish time, EF is the earliest finish time, LS is the latest start time, and ES is the earliest start time.
• Free float: This is the difference between the earliest finish time of a task and the earliest start time of the next task. The formula for free float is FF = ES – EF , where ES is the earliest start time of the next task, and EF is the earliest finish time of the current task.

To calculate float time, you need first to find the earliest and latest start and finish times for each task using a network diagram and a forward and backward pass method. Then, you can use the formulas above to find each task’s total and free float. Tasks with zero total float are on the critical path and cannot be delayed without affecting the project duration. Tasks with positive total float are not on the critical path and have some flexibility in their scheduling.

Difference Between Critical Chain Method (CCM) and Critical Path Method (CPM)

There are a few differences between the Critical Chain Method (CCM) and the Critical Path Method (CPM), but they both focus on schedule development and estimation. These are:

• Critical Path Method is focused on how long a project is based upon task estimation and the amount of float on a project.
• Critical Chain Method operates on shortening how long a project is due to overestimation, uncertainties, and buffers.

Critical Path Method (CPM) and Program Evaluation and Review Technique (PERT)

Program Evaluation and Review Technique (PERT) is a method used to examine the tasks in a schedule and determine a Critical Path Method variation  (CPM) . It analyzes the time required to complete each task and its associated dependencies to determine the minimum time to complete a project. It estimates the shortest possible time each activity will take, the most likely length of time, and the longest time that might be taken if the activity takes longer than expected.

Although CPM and PERT are conceptually similar, some significant differences exist mostly due to the type of projects best suited for each technique. PERT is better to use when there is much uncertainty and when control over time outweighs control over costs. PERT handles uncertainty of the time required to complete an activity by developing three estimates and then computing an expected time using the beta distribution. CPM is better suited for well-defined projects and activities with little uncertainty, where accurate time and resource estimates can be made. The percentage of completion of the activity can be determined. [1]

Critical Path Method History

The CPM scheduling technique was introduced at approximately the same time as PERT Analysis . It was developed by J. E. Kelly of Remington-Rand and M. R. Walker of DuPont to aid in scheduling maintenance shutdowns in chemical processing plants. Over the years, CPM has enjoyed more use than any other network scheduling technique. It is based on the concept of critical path and was designed to focus on the time and resources, particularly cost, necessary to complete a project’s activities.

AcqLinks and References:

• [1] Defense Systems Management College “Scheduling Guide for Program Managers” – Oct 2001
• Website: Project Manager.com – Ultimate Guide to the Critical Path Method

Updated: 7/13/2023

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Critical Path Method for Project Management

September 2, 2023 - 10 min read

The Critical Path Method (CPM) is a vital project management tool that represents the most extended sequence of tasks that must be accomplished to ensure the completion of the entire project.

You can determine the critical path by measuring the longest sequence of dependent activities from start to end.

It can be visually represented by using a Gantt Chart software that can help build a visual timeline of the project.

In this article, we’ll detail in depth the steps for using critical path method for project management, explain how to calculate the length of your project, explain how keeping an up-to-date project schedule allows you to have flexibility within your critical path, and share our helpful project scheduling template to get you started.

What is the critical path method?

The CPM is a sophisticated project management technique to plan, schedule, and manage complex projects. It involves identifying all the tasks needed to complete a project, determining the sequence in which these tasks must be carried out, and then calculating the most prolonged duration of time it will take to complete the project from start to finish. This most prolonged duration is known as the ‘critical path,’ and it provides a clear timeline for project completion.

In CPM, tasks are categorized as ‘critical’ and ‘non-critical.’ Critical tasks must be completed on time to ensure the project is finished on schedule. Any delay in a crucial task will result in a delay in the project. Non-critical tasks, on the other hand, have some flexibility in their scheduling so they’re less likely to cause a delay in the project completion.

CPM is especially valuable for projects with numerous interdependent activities, as it allows project managers to see where potential bottlenecks may occur and where resources can be allocated most effectively. By identifying the critical path, project managers can prioritize tasks, mitigate risks, and better ensure timely project completion.

Benefits of using critical path method in project management

CPM offers many benefits that can significantly enhance the effectiveness of project management. 

• Provide a clear visualization of the project timeline. By illustrating the sequence and duration of each task, CPM allows project managers to gain a comprehensive understanding of the project’s flow, making it easier to plan and manage resources effectively.
• CPM’s ability to identify critical tasks. This not only helps in prioritizing tasks but also allows for the proactive management of potential delays. By understanding which jobs have the flexibility to be delayed without affecting the overall timeline, project managers can better manage changes or issues that arise during the project life cycle.
• CPM aids in risk identification and mitigation. Highlighting the critical path allows project managers to foresee potential bottlenecks or delays and proactively mitigate these risks. This can lead to a significant reduction in project downtime and associated costs.
• CPM promotes better communication within the project team. With a clear visual representation of the project’s timeline, team members can better understand their roles, responsibilities, and the impact of their tasks on the overall project. This can lead to improved collaboration, efficiency, and overall project success.

In summary, the CPM is an indispensable tool in project management, offering enhanced planning, risk mitigation, resource management, and team collaboration capabilities.

How to find the critical path in a project

Step 1: Identify all tasks required to complete the project

Start by listing all the functions or activities that need to be completed for the project’s successful conclusion, also known as a work breakdown structure . When created thoroughly, the work breakdown structure is a roadmap that guides a team when completing projects — whether simple or complex. Here’s a powerful work breakdown structure example from Wrike.

Step 2: Determine the sequence of tasks

Next, identify the order in which the tasks need to be performed. Some tasks may depend on the completion of others before they can begin, while others may be carried out concurrently. This step is crucial in understanding the dependencies and relationships between tasks.

Step 3: Estimate the duration of each task

Assign a time estimate to each task. This should be the total time required to complete each task from start to finish. Make sure to account for any potential delays or issues that may arise.

Step 4: Draw a network diagram

Using the information from the previous steps, draw a network diagram. This visual representation should depict all the tasks, their sequence, and their dependencies. Each task is represented as a node on the diagram, and the arrows between nodes represent the dependencies between tasks.

Step 5: Identify the critical path

The critical path is the longest path from the start to the end of the project, passing through all the essential tasks to the project’s completion. In other words, the sequence of tasks determines the minimum time needed to complete the project. On your network diagram, the critical path is the longest from the initial to the final task.

Step 6: Calculate the float

The float or slack is how long you can delay a task without waiting for the project. Tasks on the critical path will have zero float, meaning they can only be postponed without impacting the project timeline. However, non-crucial tasks may have some float, allowing for some flexibility in scheduling.

Step 7: Monitor the critical path

Once the project is underway, closely monitoring the tasks on the critical path is essential. Any delays in these tasks will directly impact the project timeline. Regularly updating and reviewing the critical way can help identify potential issues early and keep the project on track.

Consider using Wrike’s critical path method template to augment this process further. This pre-structured template simplifies identifying your project’s critical path, saving time and enhancing project planning efficiency. 

Try our template

Critical path method example

Now we’ll try to demonstrate the concept of the critical path method with a simple, real-life example: planning a killer party. How should you plan and execute this project?

1. Define the project scope

First, we need to define all of the tasks that must be finished to complete the project. For our party example, it might look like this:

• Choose a date and venue
• Make the ultimate playlist
• Set up the sound system
• Invite your friends
• Buy the food and drinks
• Cook your famous casserole
• Host the party

When we look at these tasks individually, we realize that some of them cannot be started before the others are completed. That is, some tasks are dependent on others. We’ve designated these relationships in the table below:

The actions “invite your friends,” “buy the food and drinks,” “cook your casserole,” and “host the party” form a sequence of tasks that must be performed in a specific order, one right after the other, to ensure a successful result. Such tasks are called sequential activities.

Together with the start of our project (“choose a date and venue”), these tasks are the most critical steps in completing our project. Thus, these actions will be placed on the critical path.

2. Define different project paths

You can have more than one critical path in a project so that several paths run concurrently. This can result from multiple dependencies between tasks or separate sequences that run for the same duration.

In planning a party, various project paths will consist of tasks that need to be completed. For example, one path could involve tasks related to booking the venue, such as researching options, visiting potential locations, and finalizing the booking. Another path might focus on the catering, which includes deciding the menu, finding a caterer, and arranging the food and drink delivery. Another path could be about entertainment, involving tasks like hiring a DJ or band and planning games or activities.

While separate, each of these paths is an integral part of the overall project and must be coordinated effectively to ensure a successful party. By clearly defining these different project paths, you can better manage the tasks and timelines associated with each one.

3. Consider the resource constraints

Traditional critical path schedules in project management are based only on causal dependencies. We’ve already marked these dependencies in our plan. (e.g., it’s impossible to cook the casserole without buying the ingredients). However, a project may have limited resources that need to be taken into consideration, such as how to calculate load in resource planning. These limitations will create more dependencies, often referred to as resource constraints .

If you work on a team, you may split the project work between team members. In our example, while you’re choosing a date and venue and inviting people, one of your friends can make a playlist, and another can get the food and drinks. The tasks can be done in parallel, as in our chart above.

However, if you’re the only person responsible for the project, you have a resource constraint because you can’t be in two places at the same time. In this case, your critical path will look different.

On the chart above, we assume you first need to choose the date and venue, and only later can you make a playlist. However, depending on the project conditions, these tasks can be performed in a different order.

4. Calculate the length of your project

L et’s assume you have to do everything by yourself. We estimated the length of time each activity will take. Also, we determined the approximate start time for each task on the critical path. Here’s what we came up with:

Now, if we add up all of our critical tasks’ duration, we’ll get the approximate time we need to complete the whole project. In our case, three days and six hours, since “make the ultimate playlist” and “set up the sound system” are not on the critical path. If we add the duration to the start time, we can calculate the earliest project completion time. Understanding the CPM allows us to make this calculation quickly and accurately.

5. Leave space for flexibility

The critical path method was developed for complex but fairly predictable projects. However, in real life, we rarely get to manage such projects. Let’s say you plan to redecorate your living room with a friend.

Your task list may look like this:

• Get rid of the old furniture
• Paint the walls
• Fix the ceiling
• Install the new furniture

Your friend’s responsibilities are to:

• Choose the new curtains
• Hang the new curtains

T he curtain tasks form a sub-project and can be treated as a non-critical path. Your friend can “choose the new curtains” and “hang the new curtains” any time before the end of your project. The curtain tasks have flexibility in the start and end date, considered float. These tasks are parallel and will not be placed on the critical path. Here’s how this project would look on a Gantt chart :

If any of the parallel tasks were to be significantly delayed, it would prevent our whole project from being completed on time. Therefore, you should always keep an eye on similar tasks.

6. Adjust to the changes in the critical path

Let’s assume that choosing the curtains took our friend longer than we initially expected. This will delay the end of the project.

Our redecoration is incomplete without the new curtains, so the path that previously was non-critical becomes critical. The initial critical path changes.

To monitor your non-critical tasks, your project schedule must be current. That’s the only way you’ll know exactly where your project is at any given moment and whether it will be delivered as initially planned.

Critical path method vs. PERT

In project management, the CPM and the Program Evaluation and Review Technique (PERT) are valuable tools. However, they each have distinct characteristics and are better suited to different types of projects.

CPM is a deterministic approach that assumes a fixed time frame for each task. This makes it ideal for projects with well-known task durations and little variability, like construction or manufacturing projects. CPM focuses on the critical path, the sequence of tasks that determines the project’s shortest duration. By identifying this path, CPM allows project managers to prioritize tasks directly impacting the project’s timeline.

PERT is similar to the critical path in that they are both used to visualize the timeline and the work that must be done for a project. However, with PERT, you create three different time estimates for the project:

• The shortest possible amount of time each task will take
• The most probable amount of time
• The most extended amount of time tasks might take if things don't go as planned

This makes PERT ideal for research and development projects or any other project with uncertain task durations. While both methods help in project planning and scheduling, PERT’s ability to handle uncertainty makes it more flexible in the face of potential changes or delays. CPM’s focus on the critical path can make managing and controlling tasks critical to the project’s timeline easier.

The choice between CPM and PERT should be based on the nature of your project and the level of certainty or uncertainty in task durations. Both methods offer valuable insights that can help drive project success.

CPM success story

The Hoover Dam , constructed between 1931 and 1936, is a testament to effective project management’s power. While the critical path method hadn’t been formally defined yet, its principles were applied during the dam’s construction. 

The project had many activities, each with dependencies and timelines. The project managers had to coordinate these activities in such a way as to ensure the project was completed on time and within budget. They effectively identified the project’s critical path, focusing resources and attention on the tasks that would cause the most significant delays if not completed on time.

The Hoover Dam was completed two years ahead of schedule despite the project’s complexity. This early completion was primarily due to the effective use of what we now know as the critical path method, making it a compelling case study for successfully implementing this technique. 

This case study provides a practical example of the critical path method in action and illustrates its potential in managing large-scale, complex projects.

How Wrike can help you with your critical path management

Determining the critical path of a project isn’t exactly a quick process. That’s why we’ve designed a pre-built template for project scheduling that will help you progress through the steps of creating your critical path. Our project scheduling template allows our customers to visualize the critical path on a Gantt chart, assign tasks to team members, and drag and drop activities to ensure proper resource management. 

Ready to use Wrike for your critical path analysis?

Further reading:

Here are some further resources you can use to brush up on your critical path method knowledge:

• The Critical Path Method , Seminar, Stanford
• Explaining the Critical Path Method , U.S. Department of Health and Human Services
• The ABCs of the Critical Path Method by Harvard Business Review

How to Use a Single Gantt Chart for Multiple Projects

• When to Use a Project Calendar vs. a Gantt Chart

Occasionally we write blog posts where multiple people contribute. Since our idea of having a gladiator arena where contributors would fight to the death to win total authorship wasn’t approved by HR, this was the compromise.

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Critical path in project management explained

Making sure your project gets done on time can be difficult, but some tools can help with that. Waterfall practitioners have been using the Critical Path in project management for decades for that very reason. Now, it’s time to learn about it and apply it to your initiatives.

What is the Critical Path in project management? How to determine it? What benefits does it offer to managers? These are the questions this article will answer. So read on and learn everything about the Critical Path.

Critical Path – the introduction

Simply put, the Critical Path is the longest sequence of tasks to be completed for the project to be delivered on time. In other words: which tasks are necessary to complete the project in a given time frame?

It stems from the Critical Path Method (CPM), a modeling technique that has been in use in project management since the 1950s. This approach is used primarily in Classic endeavors.

What is the goal of the Critical Path in project management?

This tool aims to identify the specific tasks that need to finish on time so the team can deliver the project without any delay.

Additionally, the Critical Path provides managers with another set of information; a list of tasks that can be delayed without compromising the project’s deadline.

What are the benefits of using the Critical Path?

Waterfall projects tend to last a long time, which poses a set of challenges for managers. Potential delays are just one of them. Estimating which tasks are critical in advance is invaluable in any project, regardless of duration.

Applying the Critical Path in project management awards managers of Classic projects a few perks:

• provides a visualization of the project,
• helps define which elements are critical to the success of the project,
• supports the prioritization of tasks,
• highlights the necessity to schedule a project at each stage,
• helps manage available resources.

How to calculate the Critical Path in project management?

Just like a dish or a cake, the Critical Path has its recipe to make it work. Calculating the Critical Path is simple, but the actions involved require comprehensive preparation. However, they cover activities that managers perform before the project starts anyway, so it won’t burden you with much extra work.

• Specify each activity – list all the tasks of the project.
• Sequence the activities – list all dependencies between the tasks.
• Estimate the duration of each activity.
• Draw a Network Diagram – visualize the activities and their dependencies.
• Calculate Early Start and Early Finish using Forward Pass.
• Calculate Late Start and Late Finish for each activity using Backward Pass.
• Find the activities with matching Early Finish and Late Finish.
• Map out a sequence of these activities from step 7.

The steps themselves might not tell you much at first. But don’t worry; I’m going to break it all down with the help of an example.

Step 1: Specifying the activities

You must have done that countless times in your career as a project manager. After all, Classic initiatives require listing all tasks before the project launches.

Managers use a tool to visualize the scope of the project – the Work Breakdown Structure . It can serve as your point of reference in creating your list.

Our example has five activities:

• Activity A,
• Activity B,
• Activity C,
• Activity D,
• Activity E.

Naturally, most projects are much more complex. However, this short amount of activities will suffice to understand the Critical Path in project management.

Step 2: Mapping the dependencies

Oftentimes, one activity is dependent on the completion of another. Managers use visual boards to see the connections between tasks instead of simply writing them down. However, at this stage, we just need a list of connections. The visual aspect comes later. I’ve listed the dependencies of my sample project below.

Step 3: Estimating the duration of each activity

It’s difficult to predict exactly how long each task will take, but if you don’t try, you won’t even have a baseline. To keep all the essential information handy, it’s best to write down the activity list, dependencies, and durations in one place. You can use the table below for inspiration.

Step 4: Drawing a Network Diagram

The table above has all the required data, but seeing the whole picture is not that easy, is it? That’s why you need a visual tool. A simple diagram will do just fine.

The dependencies are a bit clearer, aren’t they? Now it’s time to explain a few terms: Early Start, Early Finish, Late Start, and Late Finish. These metrics are indispensable in figuring out the Critical Path.

Step 5: Calculating Early Start, Early Finish with Forward Pass

The forward pass is a technique to determine the early start (ES) and early finish (EF) of each activity, as well as the duration of the entire project. It involves adding every activity’s early starts and finishes across the whole project. Here’s how it works in practice.

Activity A has an early start (ES) of 1. After all, it’s the start of the project. It is scheduled for two days, so it will finish at the end of day two (EF=2).

Activity B starts on day 3 and lasts for 5 days, so until the end of day 7. That means ES=3 and EF=7.

The next activity – C – starts at the same time as B (day 3) and takes eight days to complete. It should end on day 10. ES=3, EF=10.

The beginning of Activity D falls on day 8 since it’s dependent on Activity B and takes two days. ES=8, EF=9.

Then, we see a complication. Activity E has two dependencies – C and D. Meaning it can only start when both are complete. The earliest Activity E can start is when Activity C is over – the one that ends later. In this case, the later one ends on day 10, so Activity E starts on day 11 and lasts until the end of day 16. ES=11, EF=16.

I’ve updated the diagram with the ES and EF values to make it more digestible.

Now we know two things:

• The duration of the entire project – 16 days.
• The Early Start and Early Finish of each activity.

One of these activities has a bit of leeway. Activity D could finish a day later, and it wouldn’t delay the beginning of Activity E. This leeway is called Float or Slack.

Step 6: Calculating Late Start and Late Finish with Backward Pass

This technique considers how late an activity can start and finish without jeopardizing the final deadline and the dependent activities. It involves going backward – from the end to the beginning – hence the name.

We know that the end of the project is in 16 days, and not a day later, so that’s our Late Finish for activity E (LF=16). It takes 6 days to complete, so the Late Start is 11.

For Activity D, the latest possible finish is on day 10, so LF=10. As a two-day endeavor, it can’t start later than day 9, which means LS=9.

Activity C has to end before E because they are connected, so the Late Finish is day 10 (LF=10). It’s scheduled for 8 days, so it cannot start later than day 3 (LF=3).

Activity B can finish as late as day 8 and begin as late as day 4. Ergo, LF=8 and LS=4. Finally, Activity A must finish on day 2 to avoid blocking the following dependent activities.

You didn’t think I would forget about another diagram, did you? Here it is, with updated Late Start and Late Finish values:

What’s the takeaway from the backward pass? It helped us determine the Late Start and Late Finish of all of the parts of the project. Also, it allowed us to spot and calculate the Float.

Steps 7 and 8: Determining the Critical Path

Now, for the moment you’ve been waiting for. To determine the Critical Path, find the tasks with the same Early and Late Finish numbers. The sequence of these tasks is the Critical Path.

In the case of our example, the Critical Path consists of activities A, C, and E. See the image below:

If you want to see the process broken down in a video format, check out the recording by Aileen Ellis, a project management certification trainer:

Critical Path in Project Management – is there a better way?

You might think: that sounds like a lot of work that I don’t have the time or energy to do. And why should you deal with that? PPM tools like BigPicture determine the Critical Path automatically. That way, you know exactly which activities in the project are crucial to its success and cannot be delayed. This knowledge can help you manage resources more precisely and prioritize surrounding tasks.

The PPM tools use Gantt chart software to visualize the Critical Path. As long as you have your scope and dependencies in the BigPicture app, you can generate the Critical Path for a Classic project with a single click. No need to do calculations on your own.

Create alternative Critical Paths with scenarios

Interestingly, BigPicture takes this functionality a step further. It combines the Critical Path with what-if scenarios . You can think of them as time simulations – what a project would look like if you changed the dates of the activities. If the new dates impact the Critical Path, it will be updated automatically based on the latest data.

The scenarios allow you to visualize the timeline based on the changes made to a project. Adding the Critical Path to your scenario provides you with another data set to make informed decisions. For instance, if you want to create an alternative path for your project and see how a delay would impact its progress.

You can store scenarios as reference points and switch between live view and the scenario in seconds. It’s helpful in presentations to quickly compare versions during meetings and plan actions with an alternative in place.

The scenarios don’t make any changes in your Jira issues until you decide to replace your live view with it. Then, all the start and dates of a scenario will transfer into the original path of your project’s Gantt chart .

Now you are ready to determine the Critical Path for your projects. Of course, with the right PPM tool, you won’t have to do any math yourself, but at least you’ll know how this method works.

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Examples of critical path method

Word of the Day

be chasing your tail

to be busy doing a lot of things but achieving very little

Binding, nailing, and gluing: talking about fastening things together

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