What does it mean if an activity in a project has zero total float?

When an activity in a project has zero total float, this indicates that any delay in completing that activity would directly impact the overall project schedule, making it critical for the activity to start and finish on time. Zero total float means there is no leeway or extra time available for that activity, so it must adhere strictly to its scheduled start and finish dates. If that activity takes longer than planned, it will delay subsequent activities and ultimately push back the project completion date.

In contrast, activities that have total float available can be delayed without any immediate repercussions on the project's timeline. Therefore, zero total float signifies that the activity is on the critical path, distinguishing it from activities that might have flexibility in their scheduling.