Float

Posted on April 28, 2010 by

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“How long can I put off starting this activity and not be in trouble?” When managing a project schedule, each activity in the schedule network diagram should have its float indicated. Float (also called slack) is how much time a certain project activity’s start can be delayed without delaying the finish date of the entire project. Think of float as the leeway or wiggle-room for doing an activity. It can be calculated as that activity’s Late Start – Early Start or as the Late Finish – Early Finish. Either formula will provide the same result.  So if activity “Paint House” will take three days to do, and it must be completed by four days after today, we do not have to start it today. We can either start painting today (then it will be done two days after today), tomorrow (then it will be done three days after today), or the day after tomorrow (then it will be done four days after today). This flexibility of having a span of three days to begin the activity is our Float. For a Critical Path Example that includes float calculation, please see the earlier posting of “Critical Path Method Explained with Cookies” (posted August 6, 2009).