Fermi question · Science
About how many kilometers is Earth’s equatorial diameter?
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
≈ 12.8 thousand kilometers
Fermi estimates are judged by scale, so a reasonable approximation can still earn a strong score.
One way to estimate it
Use Earth’s radius and double it.
- Earth radius≈ 6,400 km
- Diameter2 × radius
- Estimate2 × 6,400 ≈ 12,800 km
Keep practicing
Try another question, or return to the daily challenge to build your personal sense of scale.