The formula for the surface area of a sphere, S, in terms of its radius, r, is:

S = 4πr^{2}

**Example**

Calculate the surface area of the sphere shown below in cm^{2} to 3 sig. figs.

**Answer**

Diameter d = 8 cm

Radius r = 8 ÷ 2 = 4 cm

**Surface Area **= 4πr^{2} = 4 x π x 4^{2} = 201.06.... ≈ **201 cm ^{2} **(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.