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Free Float and Total Float in Network Diagram using Critical Path Method



What is Float (Slack)


Project management float is the amount of time a given task can be delayed without causing a delay in the entire project


Float is the amount of time an activity, network path, or project can be delayed from the early start without changing the completion date of the project. Total float is the difference between the finish date of the last activity on the critical path and the project completion date.

  • Predecessor – An activity that logically comes before a dependent activity in a schedule

  • Successor – A dependent activity that logically comes after another activity on a schedule.


Activity on Arrow (AOA)


How do you calculate float on activity? To calculate the float in AOA, subtract the task's earliest finish (EF) date and the activity duration from its latest finish (LF) date.

It looks like this:

Float = LF - ES - Duration





How do you calculate float in AOA


Activity on Node (AON)


There are 2 types of floats that exist in a PDM i.e.

  • Total Float

  • Free Float

Total Float: the amount of time an activity can be delayed or extended without extending the overall project’s completion time.

Free Float: The amount of time an activity can be delayed without delaying the early start date of its subsequent tasks.






How do you calculate float in AON




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