Answer & explanation
The official answer, with Fermi’s reasoning step by step.
Answer & explanation
Official answer
650
cities
How to estimate it
Fermi’s official “Napkin math”
The easiest place to start is the world population, about 8 billion. How many live in a city of a million or more? Maybe 1 in 4. Now, how many people live in the average one of those cities? There are some giants like Tokyo, but let's call it 3 million.
- World population
- 8,000,000,000
- Live in a 1M+ city
- ≈ 1 in 4
- Average city size
- ÷ 3,000,000
- 8B ÷ 4 ÷ 3M
- ≈ 670
Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.
Source calculation & reference
- Urban agglomerations of 1 million or more (citypopulation.de, 1 Jan 2026)
- 652
- UN World Urbanization Prospects 2018: 548 in 2018, projected 706 by 2030
- on track for ≈ 650
- ≈
- 650
Reference cited by Fermi: citypopulation.de (Thomas Brinkhoff), Major Agglomerations of the World, 1 January 2026: 652 urban agglomerations of 1 million or more · cross-check: UN World Urbanization Prospects 2018 (548 in 2018, projected 706 by 2030)
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