Calculate the Float of Each Activity on the Non-Critical Paths
The critical path activities have a float of zero. To calculate the float of each activity on the non-critical paths, you must identify the next longest path and then subtract its duration from the duration of the critical path. This will give you the float for each activity on the path being examined.
Note: When you calculate the float, it is crucial for you to calculate the float in the order of longest to the shortest.
For example, the float for Path 1 is:
Float for activities on Path 1 = Duration of critical path – Duration of Path 1
= 38 days – 19 days = 19 days
The float for each activity on Path 1 is 19 days. The Purchase Plot, Select Design, and Assemble Shed activities also lie on another path (the critical path), for which we’ve already calculated the float. Therefore, though these activities lie on Path 1, the float you will take will be that of the longer path. In other words, the float for Purchase Plot, Select Design, and Assemble Shed is not 19, but 0. This is the reason why you must calculate float from the longest path to the shortest.
Now, let’s calculate the float for the next longest path – Path 2.
Float for activities on Path 2 = Duration of critical path – Duration of Path 2
= 38 days – 17 days = 21 days