Critical Path Project Management (CPM) ExampleA simplified example of critical path project management (CPM) 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 PathMost Project Management software programs will calculate a CPM critical path for you. If the project is complex, this may be necessary. For a simple case, like this example, you can determine the critical path for yourself.
Start with the earliest task. Then see what tasks can't start until that one is finished. 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 becomes the third step in the critical path. Continue this until you reach the end of the project.
For our example project, the tasks, their dependencies, and durations are shown in the chart above. The critical path is outlined in red.
Using this task list/WBS, we see the tasks that make up the critical path are tasks 1, 2, 3, 4, 10, 11, 12, and 13. The other tasks (5, 6, 7, 8, and 9) have some extra time available to complete them if necessary. This extra time is called float.
While the smart project manager focuses on the tasks on the critical path, it is important to keep an eye on the other tasks too. If something happens to extend them, they could become critical path tasks.
Critical Path Project Management (CPM) TipsYou may be able to shorten the overall project timeline by compressing a task on the critical path. 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 that.
Keeping an eye on the other tasks is also an important project management responsibility. If one of them slips and takes longer, the project timeline might get 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, putting it on the critical path instead of task #4, installation of the plumbing, and making the entire project take longer.