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Fermi Estimation Lab

Master the art of educated guessing — the skill that separates brilliant thinkers from the rest.

"It is better to be roughly right than precisely wrong." — John Maynard Keynes (and every Fermi problem solver ever)

"Give me 30 minutes and I'll estimate anything to within a factor of 10." — Enrico Fermi, physicist & Manhattan Project legend

What is Fermi Estimation?

Fermi estimation is the art of making educated approximations to seemingly impossible questions — using nothing but logical reasoning, known facts, and comfortable arithmetic.

Google, SpaceX, McKinsey, and Jane Street all use Fermi problems in interviews to test how you think, not whether you've memorized the answer. The goal isn't to be exactly right — it's to be in the right order of magnitude.

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Break It Down

Split every big question into manageable chunks

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Powers of 10

Scored on orders of magnitude — not exact digits

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Reason First

No timers — take your time to think it through

15

15 Questions

Classic Fermi problems used in real interviews

Scoring System

Your estimate is scored by how many orders of magnitude (powers of 10) it differs from the real answer:

🏆 Spot On!	Within 2× of correct	5 pts
🎯 Close!	Within 10× (1 order)	4 pts
✅ Reasonable	Within 100× (2 orders)	3 pts
📊 In the Ballpark	Within 1,000× (3 orders)	2 pts
🤏 Wide Miss	Within 10,000× (4 orders)	1 pt
❌ Way Off	More than 4 orders off	0 pts

Question 1 of 15 Score: 0 pts

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Question text here

piano tuners

💡 Tip: commas OK — type things like 1,000,000 or 3.5e9

Question 1 of 15 Score: 0 pts

Question 1

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Spot On!

+5 points

Your Estimate

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Real Answer

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Log-scale closeness meter

Your estimate Real answer

💡 How to Think About This

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Lab Complete! 🎉

Here's how you did across all 15 Fermi problems

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Nobel Laureate

"Fermi himself would be impressed"

75

out of 75 points

All Estimates

	Question	Your Estimate	Real Answer	Pts