Answer & explanation
The official answer, with Fermi’s reasoning step by step.
Answer & explanation
Official answer
193,000
square feet
How to estimate it
Fermi’s official “Napkin math”
The easiest place to start is Earth's surface, about 200 million square miles. How much of that is land? Around 30%, shared by 8 billion people. A square mile is about 28 million square feet, so multiply up at the end.
- Earth's surface
- ≈ 200M sq mi
- 30% is land
- ≈ 60M sq mi
- 60M ÷ 8 billion people
- ≈ 0.0075 sq mi each
- × 28M sq ft in a sq mi
- ≈ 210,000 sq ft
The easiest place to start is Earth's surface, about 500 million square kilometers. How much of that is land? Around 30%, shared by 8 billion people. That works out to about 2 hectares each, and a hectare is 10,000 square meters.
- Earth's surface
- ≈ 500M km²
- 30% is land
- ≈ 150M km²
- 15B hectares ÷ 8 billion people
- ≈ 2 hectares each
- 2 hectares × 10,000
- ≈ 20,000 m²
Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.
Source calculation & reference
- Earth's land, Antarctica included (CIA World Factbook)
- 148.94M km²
- In square feet
- ≈ 1.6 quadrillion sq ft
- World population, mid-2026 (UN World Population Prospects 2024)
- ÷ 8.3 billion
- ≈
- 193,000 sq ft
Reference cited by Fermi: CIA World Factbook, 148.94M km² of land ÷ UN WPP 2024, 8.3B people (mid-2026)
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