Constraint
Scheduling Terms
Reviewed by forProject Technology - updated Sep 2026
Quick definition: In scheduling, a Constraint is an imposed or mandatory date placed on a specific task or milestone.
Constraints override the schedule's natural logic by forcing a task to start or finish on, before, or after a specific date, regardless of what its dependencies would otherwise allow. Common types in tools like Microsoft Project include "Start No Earlier Than," "Finish No Later Than," "Must Start On," and "Must Finish On."
Why it matters
A constraint that conflicts with a task's logical dependencies can distort the schedule, sometimes producing Negative Float that signals the plan may not be achievable as written. Schedulers need to use constraints sparingly and know exactly why each one is there, since overuse can hide real schedule risk.
Also known as
N/A
Used in
Network Schedule construction; Critical Path Method (CPM) calculations
FAQ
Are all scheduling constraints equally restrictive?
No — some, like "Start No Earlier Than," only set a boundary, while others, like "Must Start On," lock a task to an exact date regardless of its dependencies.
Can a constraint cause negative float?
Yes — if a constraint forces a date that conflicts with the task's logical dependencies, the schedule can calculate negative float, which flags a scheduling conflict.
Definition maintained by forProject Technology.
© 2026 forProject Technology, Inc.
© 2026 forProject Technology, Inc.
