Project Management with SAP R/3
Free float is the excess time available before the start of the following activity, assuming that both activities start on their early start date. Free float is calculated in the following way: FREE FLOAT = EARLIEST START OF FOLLOWING ACTIVITY - EARLIEST START OF PRESENT ACTIVITY - DURATION OF PRESENT ACTIVITY On the activity's calendar, free float is the length of time from the end of the activity to the earliest Early Start date from among all of its successors. If the activity has no successors, the project finish date is used. Since free float is meaningless for hammocks, it is set to zero. For the common case where all lags are finish-to-start lags of zero, the free float represents the number of work days that an activity can be delayed before it affects any other activity in the project. Example: The current activity has an Early Start of March 1st and a duration of 3 days. The succeeding activity has an Early Start of March 7th. Assuming everyday is a work day, then: FREE FLOAT = March 7 - March 1 - 3 days = 6 days - 3 days = 3 days Free float can be thought of as the amount of time an activity can expand without affecting the following activity. If the current activity takes longer to complete than its projected duration and free float combined, the following activity will be unable to begin by its earliest start date.
[vgl. netman.cit.buffalo.edu/FAQs/proj-plan.glossary.html, Project Management Glossary (28.12.2001), URL]