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.)

It is a rather complicated formula to remember, so don't worry if you need to look back at this introduction to check it out! Simply click on the red button on the right of the screen.