Critical Path Project Management (CPM)

Critical Path Project Management (CPM)

Coworkers discussing project on digital tablet
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Critical path project management (CPM) is a technique used to complete projects on time by focusing on key tasks. One path through all the inter-connected tasks is the fastest in any project. This is the critical path. By focusing on the tasks that make up the critical path, the project manager maximizes the chances of completing the project on time.

This is critical path project management (CPM).

An Example of CPM

A simplified example of critical path project management is this project plan for building a house. All the tasks in the project are listed in the Work Breakdown Structure (WBS), then the dependencies between the tasks are determined and the duration of each task is calculated.

Calculating the Critical Path

Most project management software programs will calculate a critical path for you. This may be necessary if your project is complex, but you can often determine the critical path for yourself in simple cases.

Start with the earliest task, then determine which tasks can't start until that one is completed. The longest of these tasks is the next task in the critical path. Figure out what tasks depend on completion of that second task and the longest of them then becomes the third step in the critical path. Continue this until you reach the end of the project.

The tasks, their dependencies and durations are shown in the chart above. The critical path is outlined in red. Using this task list, we can see that the tasks that make up the critical path are 1, 2, 3, 4, 10, 11, 12 and 13. You'll have some extra time to complete the other tasks – 5, 6, 7, 8 and 9 – if necessary. This extra time is called "float." It's important to keep an eye on the other tasks, too, however. They could become critical path tasks if something happens to extend them.

If one of them slips and takes longer, the project timeline may be extended. For example, if the installation of insulation in task #8 is not properly supervised and is done in the wrong places first, it might make the installation of the electrical wiring, task #5, take longer. This puts it on the critical path instead of task #4, making the entire project take longer.

Critical Path Project Management (CPM) Tips

You may be able to shorten the overall project timeline by compressing a task on the critical path. For example, task #4, installing the plumbing, is on the critical path. You can shorten that task by hiring another plumber or by having the scheduled plumber work overtime if the project budget will allow it.  

The Bottom Line

Maximize your chances of completing your project on time by calculating the critical path and managing the tasks that make it up. Just be sure that no other task slips so much that it becomes a critical path task.