Fermi question · Science
About how many kilometers across is the Sun?
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
≈ 1.4 million kilometers
Fermi estimates are judged by scale, so a reasonable approximation can still earn a strong score.
One way to estimate it
Scale from Earth’s diameter using the Sun-to-Earth size ratio.
- Earth diameter≈ 12,800 km
- Sun is roughly≈ 109 Earth diameters across
- Estimate12,800 × 109 ≈ 1.4M km
Keep practicing
Try another question, or return to the daily challenge to build your personal sense of scale.