The formula for the surface area of a sphere, S, in terms of its radius, r, is:
S = 4πr2
Example
Calculate the surface area of the sphere shown below in cm2 to 3 sig. figs.
Answer
Diameter d = 8 cm
Radius r = 8 ÷ 2 = 4 cm
Surface Area = 4πr2 = 4 x π x 42 = 201.06.... ≈ 201 cm2 (3 s.f.)