Slack
Scheduling Terms
Reviewed by forProject Technology - updated Sep 2026
Quick definition: Slack is another name for Float — the amount of time a task can be delayed before it affects other tasks or the project's finish date.
Slack is simply an alternate term for Float, used interchangeably across scheduling tools (Microsoft Project, for example, uses "Slack" where other tools say "Float"). The underlying concept, and the way it's calculated, is identical. The subtypes carry across the same way: Total Slack is Total Float, Free Slack is Free Float, and Negative Slack is Negative Float.
What this means for you
Knowing that Slack and Float mean the same thing prevents confusion when moving between different scheduling software or terminology conventions. Whichever term is used, it identifies how much scheduling cushion exists before a delay becomes a problem.
Also known as
Float (Total Float, Free Float)
Used in
Critical Path Method scheduling; Critical Path identification
See also
FAQ
Is Slack different from Float in any way?
No. They're the same concept. "Slack" is simply the term some scheduling tools, like Microsoft Project, use instead of "Float."
Does zero slack mean a task is on the Critical Path?
Generally yes — tasks with zero, or the least, float/slack in the schedule are typically on the Critical Path.
Definition maintained by forProject Technology.
© 2026 forProject Technology, Inc.
© 2026 forProject Technology, Inc.
