Scheduling Fundamentals
Total Float
Total float is the amount of time an activity can be delayed without pushing back the project's overall finish date.
Definition
Total float (sometimes called total slack) is calculated as the difference between an activity's late finish date and its early finish date (or equivalently, late start minus early start). An activity with zero total float is on the critical path -- any delay to it delays the project. An activity with 10 days of float can slip by up to 10 days before it starts affecting the finish date. Float isn't fixed: it changes between schedule updates as logic, durations, and actual progress change, which is why tracking float over time -- not just in a single snapshot -- is often more diagnostic than looking at any one update in isolation. DCMA's 14-point schedule health check flags both negative float (a logic or date problem, since float should never go below zero on a properly forecast schedule) and unusually high float (often a sign of missing logic tying that activity to the rest of the network).
Example
An activity showing 25 days of total float in January and 3 days of total float in the following month's update has genuinely become near-critical -- worth flagging even though it's still technically not driving the finish date yet.