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Total Float vs Free Float
Total float and free float refer to the amount of time, or scheduling flexibility, that exists associated with activities on the project schedule. Float may occur when there are two or more activities happening concurrently.
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). Total float is shared between the activities in a sequence. A sequence is defined as the activities between a point of path divergence and path convergence.
Total float represents the amount of time an activity can be delayed without delaying the overall project duration and is also called “float” or “slack”.
Free float is measured by subtracting the early finish (EF) of the activity from the early start (ES) of the successor activity.
Free float represents the amount of time that a schedule activity can be delayed without delaying the early start date of any immediate successor activity within the network path.
Free float is only calculated on the last activity in an activity sequence.
If activity 1.4 has a duration of 6 days and is occurring concurrently with activity 1.5 which has a duration of 9 days, activity 1.4 has 3 days of total float. Meaning, it can be delayed up to three days without any effect on the project.
However, if activity 1.4 is delayed by 5 days, there is now a negative float situation: -2 days. This reflects the fact that the project will now take two days longer than anticipated.
Total float, also called float or slack, is the amount of time an activity can be delayed without delaying the overall project duration. Total float is shared between activities in a sequence.
Free float is the amount of time an activity can be delayed without delaying the early start of any immediate successor activity.
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