Brooks's Law

Fred Brooks's principle (from The Mythical Man-Month) that 'adding manpower to a late software project makes it later.' New team members require onboarding from existing members (consuming productive capacity), communication channels grow quadratically with team size (n people need n(n-1)/2 channels), and tasks have sequential dependencies that can't be parallelized. Brooks's Law is the formal statement of why throwing bodies at a problem usually doesn't work—and it applies far beyond software to any complex knowledge work where coordination costs grow faster than capacity.

When to use it

When projects are behind schedule and the instinct is to add headcount; when growing teams aren't producing proportional output increases; when new hires seem to slow existing team members down; when deciding between adding people and reducing scope.

How it can help

When a project is behind schedule, resist the instinct to add people. Instead: (1) Reduce scope to fit the existing team's capacity. (2) Remove bottleneck tasks that are blocking parallel work. (3) Reduce coordination overhead (fewer meetings, clearer ownership). (4) If you must add people, add them to tasks that are truly independent and require minimal onboarding. The deeper lesson: plan team size correctly from the start, because adding people mid-project is almost always counterproductive for complex work.