1QUESTION 1 OF 3
Answer & explanation
The official answer, with Fermi’s reasoning step by step.
Answer & explanation
Official answer
670,000
people
How to estimate it
Fermi’s official “Napkin math”
Imagine a small town of 10,000 or so people. Is anyone 100 or older? Maybe one. Scale that up to the world's population.
- World population
- 8,000,000,000
- Aged 100 or older
- ≈ 1 in 10,000
- 8B ÷ 10,000
- ≈ 800,000
Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.
Source calculation & reference
- Centenarians worldwide in 1950 (UN)
- ≈ 15,000
- Growth to 2026
- × 45
- 15,000 × 45
- ≈ 670,000
Reference cited by Fermi: United Nations World Population Prospects, via Joseph Chamie (former UN Population Division director), IPS News, May 2026: about 672,000 centenarians in 2026
How close was your guess?
Your comparison will appear here.
Compare by ratio: divide the larger number by the smaller one. The closer to 1×, the better.