# Home > Measurement > Surface Area of Solids > Surface Area of a Sphere

# Surface Area of a Sphere The surface area of a sphere with radius r is obtained by multiplying 4, pi and radius squared.

The formula for surface area of a sphere is :

Surface Area (SA)  =  4 r2

or  SA  =  4 x x (radius)2

Example 1 : What is the surface area of a sphere with radius 15 cm?

SA  =  4 r2

=  4 x 3.14 x 152

=  2827.4 cm2 (correct to 1 decimal place)

Example 2 : What is the surface area of a sphere with diameter 22 cm?

SA  =  4 r2

=  4 x 3.14 x 112   (r = = 11 cm)

=  1519.8 cm2 (correct to 1 decimal place)

# Surface Area of a Hemisphere A hemisphere is half of a sphere, and the surface area of a hemisphere is half the surface area of a sphere.

So the formula for surface area of a hemisphere is:

Surface Area (SA)  =  2 r2

or  SA  =  2 x x (radius)2

Example 3 : What is the surface area of a hemisphere with radius 12 cm?

SA  =  2 r2

=  2 x 3.14 x 122

=  904.3 cm2 (to 1 decimal place)

Example 4 : What is the surface area of a hemisphere with diameter 36 mm?

SA  =  2 r2

=  2 x 3.14 x 182 (since r = 18 mm)

=  2034.7 mm2 (to 1 decimal place)