Fermi question · Science
About how many kilograms is the mass of Earth’s Moon?
Make a fast, defensible estimate before you reveal the reference answer. Think in factors, not exact recall.
What is your estimate?
Your result will appear here after you submit a guess.
Reference answer
Reveal the reference answer
≈ 7.35 × 10²² kilograms
Fermi estimates are judged by scale, so a reasonable approximation can still earn a strong score.
One way to estimate it
Approximate the Moon as a sphere and combine its size with rocky-body density.
- Moon radius≈ 1.74 × 10⁶ m
- Volume × density4/3πr³ × ≈ 3,300 kg/m³
- Estimate≈ 7 × 10²² kg
Keep practicing
Try another question, or return to the daily challenge to build your personal sense of scale.