HKSM

The maximum time an activity can slip without pushing the early start of any successor or breaking a schedule constraint.

Key Points

• Free float is measured for a single activity relative to its immediate successors.
• Computed as the earliest successor's early start minus the activity's early finish, adjusted for leads/lags and constraints.
• If a successor is scheduled to start as soon as this activity finishes, the free float is zero.
• Different from total float, which is based on the overall path or project finish date.

Example

Activity B finishes (EF) on day 8. Its earliest successor, Activity C, has an early start (ES) on day 10. Free float for Activity B is 2 days (10 - 8). B can be delayed up to 2 days without delaying C's early start or violating any schedule constraint.

PMP Example Question

Which statement best describes free float?

1. The total time an activity can slip without delaying the project completion date.
2. The time an activity can be delayed without delaying the early start of any successor or violating a schedule constraint.
3. The slack available to the entire network path on which the activity lies.
4. The extra time created by assigning additional resources to an activity.

Correct Answer: B — The time an activity can be delayed without pushing a successor's early start or breaking a constraint

Explanation: Free float looks only at the relationship between an activity and its successors, not the overall project finish or full path slack.