Blog
ProjectsSeptember 5, 2026· 5 min
The critical path (CPM) explained in five minutes
What the critical path is, why a two-day task can delay a six-month project, and how to watch it live.
A project isn’t late because all its tasks are late. It’s late because one critical-path task is.
The idea in one line
The critical path is the longest chain of dependent tasks. Its total length is the project’s length. If any of those tasks slips a day, the whole project slips a day.
Slack: the cushion everything else has
Tasks off the critical path have slack: they can move a little without affecting the delivery date. Knowing each task’s slack tells you where you can reassign people and where you can’t.
How it’s calculated
- Forward pass: each task’s earliest start is the latest finish among its predecessors.
- Backward pass: from delivery, each task’s latest finish is the earliest late start among its successors.
- Tasks whose early and late start match have no slack. They are the critical path.
Watch it move
MKA’s Gantt computes the critical path live. In the projects demo, tap a bar to stretch a task and watch which tasks turn red.