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Free float vs total float-Difference between free float and total float

This page on Free float vs total float describes difference between free float and total float. Float or slack is very important in project management. It is used in network diagram used for time schedule management. As mentioned below there are three types of float viz. total float, free float and project float. Figure below mentions node or activity with box to be used in network diagram. As mentioned ES(Early start), EF(Early FInish), LS(Late Start) and LF(Late Finish) is depicted in the corners. Float is mentioned in the center. Activity duration is mentioned on top of the each box.

activity float or slack

In general, the float for any activity is the amount that its duration can slip without causing the project to be delayed. It is calculated by substracting ES from LS OR by substracting EF from LF as mentioned below in the equation. The float for any activity on the critical path is zero. The critical path is the path with the longest duration.

Float = LS-ES   OR    Float = LF-EF

Total Float

Total Float is the amount of time an activity can be delayed without delaying project planned end date or any intermediate milestone if any. This is very important type of float.

Free Float

Free Float is the amount of time an activity can be delayed without delaying the early start(ES) date of its successor activity.

Project Float

Project Float is the amount of time a project can be delayed without delaying project completion date given by the customer or management. This has been committed to the stakeholders by the project manager in charge.

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