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Critical Path Method (CPM)

What is the critical path method (CPM)?

Definition of critical path method

The critical path method (CPM) is a modeling technique used by product managers to estimate how long a project will take and ensure its timely delivery.

A project’s critical path is determined by calculating the longest distance between start and finish, taking into account all tasks and their duration. The underlying forecast and scheduling paint a clear picture of what needs to be done and when. 

  • The earliest start date represents the quickest time a task can start and needs to consider all dependencies.

  • The latest start date represents the most belated moment in which a task can start (and should always be accompanied by the latest possible finish date, too).

  • Slack/float refers to how long you can delay a task without affecting the delivery of the project.

  • Crash duration describes the fastest time frame in which a task can be completed by allocating extra resources.

To identify the critical path of a project, you need to:

  1. Create a list of all your project tasks.

  2. Establish the dependencies that link your tasks.

  3. Prioritize tasks according to how critical they are.

  4. Calculate time estimates for each task.

  5. Create a Plan B in case things don’t go according to Plan A (always wise!)

General FAQ

What is the critical path method in project management?
The critical path method is a process through which project managers schedule tasks, pin-point deadlines, forecast scenarios and reveal what-ifs that help them stick to on-time delivery.
How is the critical path method calculated?
The critical path method is calculated in two steps. First, product managers estimate the longest distance from start to finish. Then, they calculate the shortest time frame needed for completion. Overlaying the two scenarios reveals the slack time available for each task.
Why is the critical path method used?
The critical path method is used by product managers to map out tasks based on importance and give more precise estimates.
Who developed the critical path method?
A pair of mathematicians at the DuPont Company developed CPM in 1957 as a way to avoid costs caused by inefficient scheduling.
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