What the Critical Path Is
The critical path is generally the longest sequence of dependent tasks that determines a project’s earliest possible finish date. Activities on this path usually have zero total float, so delays here will likely delay the overall project. Managers typically map tasks, durations, and dependencies to reveal the network of paths through the work. Among those paths, the one with the greatest total duration is commonly called “critical,” and others may be near-critical with small amounts of float.
The critical path is the longest dependency chain that most directly governs the project’s finish date.
How to Calculate It
You would usually list all activities, estimate durations, and define finish-to-start and other dependency types before drawing a network diagram. A forward pass estimates earliest start and finish dates, while a backward pass derives latest start and finish, revealing total float. Tasks with effectively zero float are treated as critical, and there can occasionally be multiple concurrent critical paths. Many teams use scheduling software to automate these passes, though a simple spreadsheet can work for smaller efforts.
Forward and backward passes across a task network typically identify zero-float activities that form the critical path.
Why Critical Paths Change
As estimates evolve and actuals come in, the critical path often shifts to reflect new realities. Calendar choices, constraints, leads/lags, or added scope can subtly re-route dependencies and move “criticality” to different tasks. Resource limits may also extend durations and create a resource-critical path that differs from the purely logical one. Near-critical chains with low float can become critical quickly when risks materialize.
Updates to scope, calendars, constraints, and resources can readily move criticality from one path to another.
Techniques to Shorten It
Teams commonly consider fast-tracking (doing some tasks in parallel) or crashing (adding resources to shorten durations), each with trade-offs. Re-sequencing work to reduce path length, removing artificial constraints, and refining over-padded estimates can also help. Scope pruning or moving non-essential features to later releases may be appropriate when deadlines are firm. Each option should be vetted for increased risk, cost, or quality impacts before adoption.
Schedule compression typically blends fast-tracking, crashing, and re-sequencing while balancing risk, cost, and quality.
Putting It to Work
In practice, critical path analysis can guide status meetings, risk registers, and stakeholder updates with concrete, time-bound focus. It helps teams prioritize mitigations on the tasks most likely to affect the end date and set realistic buffers around near-critical chains. Leaders can also use it to test “what-if” scenarios before committing to dates or budgets. Applied thoughtfully, it becomes a repeatable way to steer delivery under uncertainty.
Using the critical path to drive decisions helps teams focus on what most influences the finish date and deliver more predictably.
Helpful Links
Wikipedia – Critical Path Method overview: https://en.wikipedia.org/wiki/Critical_path_method
Atlassian – Intro to the Critical Path Method: https://www.atlassian.com/work-management/project-management/critical-path-method
Smartsheet – Critical Path Method Guide: https://www.smartsheet.com/critical-path-method
Microsoft Support – Show the critical path in Project: https://support.microsoft.com/en-us/office/show-the-critical-path-of-a-project-7f3f2e68-157c-41f1-b014-1350d63b07fc
Lucidchart – Critical Path Method explanation: https://www.lucidchart.com/blog/critical-path-method