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Backward Pass

Backward Pass

Scheduling Terms Reviewed by forProject Technology - updated Sep 2026
Quick definition: The Backward Pass is the schedule calculation that works back from the project finish date, following the links between tasks in reverse, to determine the latest each task can start and finish without delaying the project.

The Backward Pass starts at the project finish date and works through the schedule in reverse, following the same dependencies the other way. A task's Late Finish Date is set by the start of the tasks that follow it, and its Late Start Date is that Late Finish Date minus the task's duration. Where several tasks follow, the earliest of them governs — the task must finish in time for the most demanding successor. Comparing these late dates against the early dates from the Forward Pass produces Total Float: how much each task can slip without pushing out the project finish. The tasks with the least float form the Critical Path.

Why it matters

The Backward Pass is what turns a set of early dates into a measure of schedule risk. Without it there is no Total Float, and without float there is no way to tell which tasks have room to slip and which ones will move the finish date. It is also where negative float first appears, signaling that a required date can no longer be met as the schedule is currently built.

Also known as
N/A
Used in
Critical Path Method (CPM) schedule calculation; Late Start Date and Late Finish Date determination; Total Float and Critical Path identification

FAQ

What does the Backward Pass actually calculate?
The Late Start Date and Late Finish Date for every task, working from the project finish date backward through each dependency in turn.
Why does the Backward Pass matter if the Forward Pass already produced a finish date?
Because the early dates alone show only when work could happen, not how much room there is for it to slip. Subtracting the early dates from the late dates gives Total Float, which is what identifies the Critical Path and exposes any task already running against a required date.
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