Enter the early finish date of the activity and the early start date of the successor activity into the calculator to determine the free float (in days).
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Free Float Formula
The following formula is used to calculate the number of days of free float.
FF = ES_{succ} - EF- Where FF is the free float (days)
- ESsucc is the early start of the successor activity (date or day number)
- EF is the early finish of the activity (date or day number)
To calculate free float, subtract the activity’s early finish from the successor activity’s early start (often using the earliest early start among all immediate successors).
Free Float Definition
Free float is the amount of time an activity can be delayed without delaying the early start of any of its immediate successor activities; it is the difference between the successor’s early start and the activity’s early finish.
Free Float Example
How to calculate free float?
- First, determine the activity early finish (EF).
Using the project network logic (e.g., a forward pass), find the earliest date/day the activity can finish.
- Next, determine the successor early start (ES).
Using the same network logic, find the earliest date/day the immediate successor can start (if there are multiple successors, use the earliest ES among them).
- Finally, calculate the free float (FF).
Subtract the activity EF from the successor ES: FF = ES(successor) − EF(activity).
FAQ
Free float is a measure of the time that a scheduled activity can be delayed without delaying the early start of any immediate successor activity.
