Critical path
Definition
The critical path is the longest chain of dependent tasks in a project network. Any delay to a task on the critical path delays the entire project by the same amount.
Critical Path Method (CPM) was developed in the late 1950s alongside PERT, though CPM assumes deterministic task durations where PERT embraces uncertainty. Together they form the foundation of modern project scheduling.
To find the critical path, you map all tasks and their dependencies, calculate the earliest start and finish times for each task (forward pass), then calculate the latest start and finish times that won't delay the project (backward pass). Tasks with zero 'float' (no slack between earliest and latest times) are on the critical path.
Knowing the critical path tells a project manager where to focus. Tasks not on the critical path have float — they can slip without affecting the deadline. Tasks on the critical path have zero tolerance. This distinction is the basis for resource allocation decisions: add resources to critical path tasks to accelerate the project; moving resources away from float tasks doesn't help the deadline.
In whiteboard sessions, teams often sketch a network diagram and then mark or highlight what they believe is the critical path. BoardSnap AI reads that structure and the annotations to produce a summary of the key dependencies and constraints.
Examples
- In a product launch: Design → Dev → QA → Deploy is critical; Documentation can slip two weeks without impact
- In a construction project: Foundation → Framing → Roof is critical; Landscaping has three weeks of float
- In an event: Venue booking is critical (12-week lead time); Swag ordering has four weeks of float
- In a software sprint: Backend API is on the critical path; Frontend can't ship without it, so frontend testing has no float
Related terms
Snap a critical path. Ship its actions.
BoardSnap turns any whiteboard — including this one — into a summary and action plan.