HKSM

The maximum time an activity can start later or take longer, relative to its early start, without pushing the overall project finish date or breaking any imposed schedule constraints.

Key Points

• Indicates schedule flexibility that does not change the project's completion date or violate constraints.
• Calculated as LS - ES or LF - EF in the network schedule.
• Activities on the critical path typically have zero total float; negative float signals the plan cannot meet a required date.
• Float on a path is shared by its activities; using it on one activity reduces what is available to others on the same path.

Example

Activity B has ES = day 5 and EF = day 9. Its LS = day 7 and LF = day 11. Total float = LS - ES = 2 days (or LF - EF = 2 days). B can start up to two days late or run two days longer without moving the project's finish or breaking a constraint.

PMP Example Question

A task shows a total float of 3 days. What does this allow the project manager to do?

1. Delay the task by up to 3 days without affecting the project finish date.
2. Delay the task by up to 3 days without affecting any successor's early start.
3. Add 3 days of scope to the task without any impact.
4. Crash the task by 3 days with no additional cost.

Correct Answer: A — Delay the task without moving the project completion date

Explanation: Total float is the time an activity can slip or extend relative to its early start without changing the project finish date or violating schedule constraints. Option B describes free float.