Fermi Estimates

Estimating almost anything

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Break hard estimates into easy factors and multiply.
• Keep track of powers of ten. Aim to be within a factor of 10.
• Over- and under-estimates tend to cancel.

Steps

1. Heartbeats
2. The Fermi method
3. Piano tuners
4. Words in a year
5. Why errors cancel
6. Build your own estimate
7. Water in a lifetime