Critical Path Method

Woman on laptop using the critical path method

What is the Critical Path Method?

The Critical Path Method is a project management methodology for modeling the timeline of a project. Engineers at Du Pont developed the critical path method in the 1950s, and it has since evolved to its modern digitized form.

The first step in implementing the Critical Path Method in project management is to list all tasks and activities required to complete the project. Next, estimate the time to complete each task. Finally, consider task dependencies so that tasks can be arranged in an appropriate order when such dependencies exist. Tasks that are not dependent on other tasks can be completed in parallel. In the end, the timeline that passes through the longest chain of dependent tasks is known as the “critical path.” 

Common terminology used when describing the Critical Path Method are as follows:

  • Dependent tasks: You cannot start these tasks until completing a previous (predecessor) task. 

  • Predecessor tasks: You must complete these tasks before starting another (dependent) task.

  • Float: This is a measure of how long you can delay a task without impacting the completion date. Generally, tasks on the critical path do not have any float.

  • Crash: This is the shortest amount of time that you can complete a particular task. Often, to complete a task within this minimum time, you may need to take shortcuts, which can diminish quality, so “crashing” a task is typically only considered if necessary to meet an important deadline.

  • Critical path: This is the longest (in terms of time) string of dependent tasks that you must complete for project completion. The length or time duration of the critical path determines the duration of the project.

  • Critical tasks: Tasks on the critical path are called critical tasks, and changes in the duration of such tasks will usually directly affect the overall project timeline.

  • Noncritical tasks: These tasks are not on the critical path. Often, delays or changes in the duration of such tasks will not impact the overall project deadline.

  • Subcritical path: In addition to the critical path, there may be other chains of dependent tasks of a shorter overall duration. These are called subcritical paths.


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Benefits of the Critical Path Method in project management.

The critical path method can help a project managers and their teams with many essential aspects of project management, including:

  • Identifying and addressing bottlenecks: By mapping out the critical path for a project, it becomes easier to see dependencies and determine which critical tasks may be at risk of delay should you fail to complete predecessor tasks in time. By making such identifications, you can quickly determine how to assign tasks and make sure you start predecessor tasks early enough to avoid potential bottlenecks. 

  • Using resources efficiently: Viewing task dependencies can also clarify how you should manage resources to tackle certain problems and when. If predecessor tasks run the risk of holding things up down the line, you can allocate resources to these first and then address noncritical tasks that have plenty of float time later on. 

  • Generating realistic timelines: Once the critical path is isolated, the project timeline will fall into place. You can clearly see the minimum amount of time needed to tackle the longest chain of dependent tasks.

  • Accelerating progress and increasing efficiency: In generating a critical path diagram, areas where you can increase efficiency may also become apparent. You may find that the critical path was not as long as you expected and that by running subcritical paths in parallel instead of sequentially, you can meet an earlier deadline. 

  • Identifying and reconsidering nonessential steps: Certainly, tasks on the critical path are essential, and many noncritical tasks might be as well, but you may also find in your analysis that you can compact or omit certain steps. 


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How to use the critical path method.

While managers once implemented the Critical Path Method manually and composed representations by hand, work management solutions like Workfront can now expedite critical path calculations and representations. However, it is still essential to conceive of your project’s components accurately to input correct data.

1. Identify all tasks.

Create a master list of all the tasks that you must complete as part of the project. It might help to break things down in hierarchical steps, considering the final deliverables first and then determining what you require for their creation. 

For example, suppose you are upgrading the computers in an office. You will need to decide on a vendor; purchase new machines; make appointments with each individual receiving a new device; perform format, imaging, and other IT services during the transition; and so on.   

2. Determine time requirements for all tasks.

For each task identified, determine the time it will take to complete. If these are tasks that have been done before on previous projects, you can use past data to determine expected times. If there is uncertainty in the time, you may want to include a time range that can later be adjusted as needed. If materials need to be purchased and shipped, you will need to factor that into the timeline, as well.

3. Identify all dependencies between tasks.

While some tasks may be doable in isolation, you will likely have several tasks you cannot perform until you complete another task. For example, a manuscript cannot pass through the editing phase until after you write it. Accompanying graphics may require at least an outline first, as well.

4. Generate a critical path diagram.

Once you have the tasks, their time requirements, and a clear idea of dependencies, you can start diagraming everything out. You may represent each task as a circle or an icon, and then utilize lines or arrows to link dependent tasks together in chains. In some cases, chains may cross each other or interact in complex ways. 

For example, If the project involves building a house, there may be a critical path that starts with pulling the permits and laying the foundation and ends with the finishing fixtures in the interior. However, you can complete tasks such as applying the roofing and outdoor siding in parallel once the basic structure of the house is in place.

5. Determine the critical path.

Once you’ve created your diagram, you can use your timeline information to determine which chain of dependent tasks will take the longest time to complete from start to finish. This is your critical path, and it will determine the ultimate timeline of the project. 

It is possible to have more than one critical path, and each of them may also have shorter dependency chains, called subcritical paths.

6. Consider floats and resource allocations.

To meet project deadlines, you’ll want to consider how you order all tasks, not just those on the critical path. There may be certain critical tasks that require more resources at the beginning of the project but less toward the end, so you can delay noncritical tasks with floats. 

Of course, it is also possible for the opposite to happen—later critical tasks may require more manpower than earlier ones. In such a situation, it makes sense to complete noncritical tasks earlier in the process so that you can allocate resources appropriately later. 

Find the critical path for your next project.

The Critical Path Method can help you visualize your overall project scope, determine a reasonable timeline, and identify ways to optimize and allocate resources efficiently. It’s a great tool to include in your project management toolbox.

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