Total float, also called float or slack, is the amount of time that a schedule activity can be delayed or extended from its early start date without delaying the project finish date or violating a schedule constraint.

Total Float = LF – EF (or LS – ES).

Total float is measured as the difference between the early and late start dates (LS - ES) or the early and late finish dates (LF – EF) where ES = Early Start, EF = Early Finish, LS = Late Start, LF = Late Finish.

On a critical path, the total float is zero. Total float is often known as the slack.