Work out sphere surface area instantly with clear inputs, formula shown and shareable results.
A sphere's surface area is 4πr², exactly four times the area of its great circle — a result Archimedes proved and asked to have carved on his tomb.
Surface area
S = 4πr² = πd²
Great circle
A = πr²
4π × 25 = 100π ≈ 314.159265 square units.
Yes. Substituting r = d/2 into 4πr² gives πd².