Critical Path DRAG (Devaux's Removed Activity Gauge) is the amount of time that an activity on the critical path (i.e., the longest path through the project) is adding to the project’s duration or, alternatively, the amount of time by which the project completion would be pulled in by reducing a critical path activity’s duration to zero. 

Activities that are not on the critical path are said to have total float or slack, i.e., the amount of time they can slip without making the project longer.  Conversely, only critical path activities and delays (such as lags or constraints have DRAG.   

1. DRAG can be computed in the following manner:
2. If an activity has nothing in parallel, its DRAG is equal to its duration.

If an activity has other paths in parallel, its DRAG is whichever is less: its duration or the total float of the parallel activity with the least total float.

There are four commercially available software packages that compute DRAG:

• Asta Powerproject v14.02+
• Spider Project.
• PlanontheNet.com
• Sumatra.com's Project Optimizer, which is an add-on to Microsoft Project.

DRAG has a corollary cost effect called DRAG Cost, which is the amount by which project profit is decreased due to an activity’s DRAG reducing the value of the deliverable and/or increasing project cost through indirect costs attached to level-of-effort activities or overhead.