Answer & explanation
Counting every dynasty's wall added together, not just the Ming.
The official answer, with Fermi’s reasoning step by step.
Answer & explanation
Official answer
502
marathons
How to estimate it
Fermi’s official “Napkin math”
The wall runs from the sea near Beijing out into the desert, about half of China's 5,000 kilometers. It climbs mountains and branches off, so call one wall three times that. And several dynasties built their own. How many? Call it three.
- Sea to desert, half of China
- ≈ 2,500 km
- Winds and branches
- × 3
- Several dynasties' walls
- × 3
- 22,500 ÷ 42 km
- ≈ 540 marathons
China is about as wide as the US, 3,000 miles. The wall runs from the sea near Beijing out into the desert, about half of that. It climbs mountains and branches off, so call one wall three times that. And several dynasties built their own. How many? Call it three.
- Sea to desert, half of China
- ≈ 1,500 mi
- Winds and branches
- × 3
- Several dynasties' walls
- × 3
- 13,500 ÷ 26 mi
- ≈ 520 marathons
Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.
Source calculation & reference
- Great Wall length, all dynasties combined (2012 government survey)
- 21,196 km
- Length of one marathon
- ÷ 42.195 km
- 21,196 ÷ 42.195
- ≈ 502 marathons
Reference cited by Fermi: China's State Administration of Cultural Heritage, 2012 national Great Wall survey
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