Fermi Estimation

Table of Contents

• Workflow
• Common Patterns
• Guardrails
• Quick Reference

Example

Question: How many piano tuners are in Chicago?

Decomposition:

1. Chicago ~3M people ÷ 3/household = 1M households
2. ~1 in 20 has piano = 50,000 pianos, tuned once/year
3. Tuner: 250 days/year × 4 tunings/day = 1,000/year
4. 50,000 ÷ 1,000 = ~50 piano tuners (Actual: ~80-100, within order of magnitude)

Workflow