Fermi estimation

Enrico Fermi was known for estimating quantities nobody could look up, like how many piano tuners work in Chicago, by breaking them into parts he could guess. Getting within a factor of a few is the skill, and it gets better with practice and feedback.

50 questions · type 40k, 2.5 million or 3e9 · enter to continue

10 questions you can't look up. Give your best number; what counts is the order of magnitude. Within 1.8× scores 3, within 3.2× scores 2, within 10× scores 1. Then see how an expert would have broken it down.

Best: …
Typical miss: …
Streak: …