What Is Critical Path Method? Definition & Examples

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critical path method

What Is the Critical Path Method?

Critical Path Method Definition

Critical path method or CPM is a technique where product and project managers identify necessary tasks to finish a project. After that, they undermine the scheduling flexibilities. The critical path method helps identify the essential tasks, dependencies, and task durations. Because if there are any delays, the entire project goes for a toss. 

Product managers and project managers commonly use the critical path method to estimate the time a particular project will take and ensure that they deliver the tasks on time. 

Pro tip: Product managers can use product management software to track and craft amazing products. 

Most often, the managers measure the critical path of any project by calculating the time that teams will utilize between the starting and the ending point. It considers all the subtasks (if any) and their duration. 

Such a prediction clarifies what and when you need to do certain things. 

Following are a few key terms that are helpful to understanding the Critical Path Method better: 

The earliest start date refers to the earliest time at which a given task can begin considering all the other subsidiaries. 

The latest start date is the opposite of the earliest start date, which refers to the maximum limit of when a particular task can start. You must accompany this by the latest finish date. 

The slack/float refers to the buffer period, or delays businesses can excuse without affecting the project’s delivery. 

The crash duration is the quickest duration within which you can complete a task by allotting extra resources. 

What Is the Critical Path Method in Project Management?

The success of an organization depends on project management. Usually, you need to complete specific tasks in parallel or sequence to complete a project. 

Managing tasks efficiently and getting to the end goal with a ready project requires effort and time. 

Therefore it is essential to understand each task and its relation.

As you know that even if one task gets disrupted or delayed, there will be a domino effect on the entire project. 

The project management team must carefully understand each activity and its impact on the entire project.

In project management, the critical path method is mainly helpful for optimizing the allocation of resources.

Doing so helps create an algorithm of activities that project teams can use to monitor how well the project is progressing.

Dependencies will differ for every activity.  

Before you calculate the critical path, you just have the following ready:

  • All the project tasks from start to end
  • The tasks dependencies
  •  An estimation of the time needed to complete a particular task

Once you have all the needed data, you can calculate the critical path. 

As we know, projects have a lot of tasks, and challenging projects have thousands of them.

It is necessary to identify the tasks that can derail the project in such cases.

And at this point, the critical path method comes in handy for project management.

The critical path method in project management will identify these tasks and ensure no delays.  

You can use various project management tools that provide advanced critical path results.

History of Critical Path Method

Morgan R. Walker and James E. Kelley developed the critical path method in the late 1950s. 

The critical path method has its basis in the Program Evaluation and Review Technique (PERT). PERT is a method similar to CPM, and product managers mainly use it along with CPM. 

The development of the critical path method came when it was necessary to clear the issue of costs.

These costs were increasing due to scheduling inefficiency. 

Ever since the development of the critical path method, product managers can now manage tasks efficiently and effectively. Not just that, but they can prioritize the essential tasks and plan projects accordingly. 

How To Find a Critical Path?

There are six steps to find a critical path:

Dividing the project into tasks/activities

To begin with, make a thorough list of your tasks. Now give each task a name or a shortcode.

Identifying and ordering the dependencies

Now put your tasks in a logical order. And identity the dependencies.  

Note that there are three types of dependencies in a project. 

  • Mandatory dependencies

These dependencies are due to the physical limitations of the tasks.

  • Discretionary dependencies

These dependencies are due to be decisions taken by the teams during the project.

  • External dependencies

These are third-party dependencies. For example, the needs of a shareholder.

Creating the network diagram

Now craft your tasks line up visually. You can do it with the traditional method of pen and paper. However, using the advanced methods available today can help you manage tasks better. 

You need to create boxes for each task and add arrows to show the dependencies. 

You can use the Gantt chart or PERT also. 

Estimating the duration

You must clearly define the start and the finish date for every task. 

You must also look at the order and dependencies and set the estimated timelines accordingly. 

You can also use the forward pass and the backward pass technique to calculate the critical path.

Leveling of resources

It is necessary to level the resources to avoid resource conflicts. 

The resource leveling step will allow you to allocate the resources efficiently, thereby completing the project in the given period.

Resource conflicts are common and can lead to:

  • Delay in task completion
  • Challenge in assigning the resources
  • Difficulty in changing task dependencies
  • Delays in projects and jumping over budget

Determining the critical path

The longest duration path is the critical path. 

Instead of calculating it manually, you can use the project management software or critical path algorithm. 

To find a critical path manually, take the below three steps:

  • Next to each activity, write the start and the end time of that activity. Do this for all the tasks
  • Now have a look at the end time of the last activity to know the duration of the entire sequence
  •  Finally, find the sequence with the longest period to get the critical path. 

What Are Examples of the Critical Path Method?

By keeping the above steps of how to find a critical path, we will look at an example of the critical path.

In the first step of Listing down activities, let’s say the task of the marketing team is to produce a new blog post that is interactive.

In the breakdown structure, we can put tasks as below:

Task A: Creating an outline: will require one day 

Task B: Writing draft: 5 days 

Task C: Editing and creating the final draft: 2 days 

Task D: Designing post visuals: need four days

Task E: Adding animations to the visuals: 2 days

Task F: Uploading the post: 1 day 

In the next step of identifying the task dependencies. In our example, the marketing team dependencies are:

Task B will be dependent on A

Task C will be dependent on B 

Tasks C and D can work simultaneously

Task E will be  dependent on D

Task F will be dependent on C, D, and E

Once we create the network diagram, a flowchart that will display the activities in chronological order, the marketing team will also have to estimate the task duration. 

Finally, plot the activities you will get the critical path. 

For our example of the critical path, the picture will be somewhat like this:

  1. Start —-> task A( need 3 days) —–> finish 
  2. Start —-> task B( need 4 days) and task C( need 3 days) —-> finish
  3. Start —-> task D( need 2 days), task E( need 4 days) and task F( need 1 day) —-> finish

In our critical path example, we have the third point of 3 tasks: task D, task E, and task F. The reason for choosing the third point as the critical path is that the longest path is the critical path. 

Now you can build the project schedule around the critical path. 

What Are the Limitations of the Critical Path Method?

  • Sometimes it is difficult to find the critical path in the critical path method
  • You need to calculate the critical path precisely when calculating the CPM
  • For challenging projects, the critical path method can get complicated
  • The critical path method doesn’t estimate the completion time of tasks or activities
  • The critical path method doesn’t support the projects that improvise a lot
  • A critical path method takes up a lot of time
  •  The critical path method assumes that every organization has the resources needed for a project. That is not always the case
  • Teams can often misuse the float in the critical path method
  • Product managers can’t include the noncritical activities in the critical path method
  • The estimates that the critical path method provides do not have the basis in the statistical analysis 


What is the float in the critical path method?

Float in the critical path method refers to the time a specific activity, project, or network path can be delayed from the start date without changing the project’s completion date

Why is the critical path method important?

Critical path method estimates the time a particular project will take and ensures that they deliver the concerned tasks on time. 

It clarifies what and when one needs to work on the projects. Moreover, it can also help accommodate and adjust any delays or unexpected circumstances during the work process.

Where is the critical path method used?

You can use the critical path method in all forms of projects. These projects can range from construction, aerospace, defense, and research projects, to product development, engineering, software development, plant maintenance, and so on.

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