Team Scaling Fallacy Calculator (Brook’s Law)

A blunt model that shows why adding engineers often slows delivery. It makes onboarding and coordination costs visible.

Inputs

How long before a new hire is meaningfully productive in this codebase.
Typical range is 10 to 35 for real teams.
Who absorbs onboarding, reviews, and decision load.
Conservative default. Increase if the system is messy.

This is a simple model. It does not assume bad hires. It assumes coordination rises with team size and that onboarding consumes senior time.

Results

Click calculate to see results.
Effective output before
0.0
Units are relative, not hours. Think of this as effective engineers.
Effective output after
0.0
Onboarding load absorbed by senior team
0 hours
Coordination drag increase
+0%
Why this happened
Summary
Talk through options

Why adding engineers can slow delivery (Brook’s Law)

  • Onboarding steals senior time: seniors stop shipping to unblock, review, and transfer context.
  • Communication paths explode: more people means more coordination, more meetings, and more waiting.
  • Context switching increases defects: quality drops, rework rises, and velocity feels worse.

This calculator makes those costs visible. It is a planning tool, not a promise.

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