Critical Path
The longest chain of dependent tasks in a project network, whose duration sets the shortest possible total project duration.
In network planning, a project is broken down into individual tasks and their dependencies. The critical path is the chain of tasks that together produces the longest lead time. This length determines the earliest possible completion date of the whole project.
Tasks on the critical path have no scheduling slack, a so-called total float of zero. If any of these tasks slips by even a single day, the entire project end date shifts by the same amount unless countermeasures are taken. Tasks outside the critical path, by contrast, carry float and can shift within that margin without endangering the deadline.
For project control, the critical path is therefore the most important lever: anyone wanting to shorten the project duration must act on tasks that sit on the critical path, for example through additional resources or by running work in parallel instead of in sequence. Measures applied to non-critical tasks barely speed up the overall project.
Formula
Total float TF = LST - EST; on the critical path TF = 0
Practical Example
When installing a new production line, the chain of foundation work, machine delivery, assembly, and commissioning takes twelve weeks in total and thus sets the earliest possible production start date. Operator training runs in parallel and takes only four weeks, leaving eight weeks of float; it is not on the critical path.
How Leanshift Helps
Knowing the critical path means directing energy to where it actually has an effect, instead of trying to optimise everything at once. That same principle, finding the lever that matters, runs through every process improvement effort.
Frequently Asked Questions
Can a project have more than one critical path?
Yes, if several chains of tasks reach exactly the same longest duration, multiple critical paths exist at the same time.
Why does the critical path lose value if it isn't kept up to date?
The critical path can shift as the project progresses whenever tasks slip or speed up, so the network plan needs to be recalculated regularly.