There are a lot of different methods of software development designed to improve the efficiency of work using a variety of tools. If you need to deal with timing and resources, you should take a closer look at the critical path method.

What CPM is 

In 1957 critical path method was created by participants of a large-scale project to restart chemical plants in the US. After that it was spread to the spheres of agriculture, construction, industry, and software development.

CPM is about the distribution of tasks in a logical order and completing them during a specified time. You need to plan, manage, and analyze the duration of the project as this way you can avoid time-related risks.

CPM is based on the idea that project tasks are performed step by step, and you can start a new task only after finishing the previous one. This sequence is called the critical path. The project manager can optimize processes with low priority in order to concentrate time and resources on critical path work. 

How to draw CPM

The critical path method represents a project as an interconnected network of tasks. During its preparation, you should adhere to the following sequence.

  • Define the scope of work

Create a list of project tasks with names or code marks and specify their duration.

  • Establish the sequence

You should set the right dependencies between steps as it will be the basis of the project.

  • Draw a graph 

Present the project as a path analysis diagram or network. Illustrate dependencies between tasks using arrows and lines.

  • Calculate the tasks’ execution time

If you know the timing of each task, you can set the duration of the whole project.

  • Find the critical path

Create the sequence of your critical path using definitions of an early and late start and finish.

Early finish: the closest data when the task can be completed, amounts to the Early Start plus duration.

Early start: the nearest data when a task can be started in the current situation.

Late finish: the latest time when the task can be completed.

Late start: the latest time when the task can be started, amounts to the Late Finish minus duration.

  • Update the scheme

Actualize your scheme if the critical path was changed.

Warning! Limited resources

Different circumstances can affect the deadline of the project and lead to additional tasks.

If your work team becomes smaller, it can lead to postponing the rollout of the project. Your critical path is, in fact, the critical amount of resources since they directly affect the result.

Pros and cons of the Critical Path Method

This project management method offers a number of perks for its users. For instance, it allows you to: 

  • represent the project as a clear graphical structure;
  • appoint key tasks for the team;
  • highlight the most important moments;
  • optimize time and resources;
  • compare the expected result with the current situation;
  • make direct links between tasks.

As the main drawback of CPM, we can mention that it was created for complicated projects with fixed deadlines. This structure won’t be perfect for projects with flexible conditions.

Besides, there are PERT Diagrams that involve changing the terms of every task.

CPM in action

As an example of managing a  project with CPM, let’s imagine that we need to build a house. There are six  tasks to complete:

  • clear the area
  • pour the foundation
  • build walls
  • build a roof
  • connect the water supply 
  • connect the electricity

Let’s set deadlines for every task:

  • prepare the area – 5 days
  • dig and pour the foundation – 15 days
  • build walls – 20 days
  • build a roof – 10 days
  • connect water supply – 5 days
  • connect the electricity – 5 days

We see that almost all these stages depend on the previous ones, and the first four tasks are basic for the following ones. We can mix steps 5 and 6, but the first four must go in the beginning. This is the critical path of the project.

You can make your CPM using special programs and tools, even Excel diagrams that will be illustrative and clear.

The Critical Path Method is an effective tool that can help you create a hierarchical structure with definite tasks, links, and duration, as well as optimize time and resources, foresee the risks, and predict the results.

Do you use CPM? Feel free to share your experience in the comments below.