Project float, also known as slack, is the amount of time by which a given task within a project can be delayed before it impacts the deadline for the project.
Project managers and developers use project float time to schedule the specific timing of tasks as well as the time frames for making decisions to best ensure that projects come in on time. Total float is the span of time between the target end date of the last task on the critical path and the target date for project completion. Free float is the time an individual task can be delayed before impacting the task that follows it, defined as the difference between the task’s earliest and latest possible finish dates.
Float can allow more time for working on a task when necessary. Otherwise, resources can be repurposed for another task. Employees working with multiple teams can put more time into other tasks that are lagging.
Total float is often represented as a positive or negative number representing the number of days. Negative float, also known as negative slack, is the amount of time beyond a project’s scheduled completion that a task requires.
See a video demonstration of using the critical path method (CPM) to find float: