📊 Slack Time Calculator
Calculate a project task’s slack time (float) using early and late start and finish dates from your schedule network.
What slack time (float) means
In project scheduling (the Critical Path Method), slack time — also called float — is the amount a task can be delayed without pushing back the overall project finish date. A task with zero slack is on the ‘critical path’ and has no room for delay.
How this calculator works
Slack is calculated as either Late Start minus Early Start, or equivalently Late Finish minus Early Finish, from your project network diagram. Enter all four values from your schedule and the calculator computes both versions and averages them, flagging the task as critical when slack is at or near zero.
This tool is for general project planning and education; real-world scheduling software accounts for resource constraints and dependencies beyond this simple float calculation.