Geometry
Surface area of a sphere
Four times the area of the circle that cuts the sphere through its centre. Note the square rather than the cube.
The Formula
A = 4 x pi x r^2
Four times the area of the circle that cuts the sphere through its centre. Note the square rather than the cube.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| A | Surface area | square units | The area of the sphere's outer skin. |
| r | Radius | linear units | Distance from the centre to the surface. |
What Each Symbol Means
Asquare units
Surface area
The area of the sphere's outer skin.
rlinear units
Radius
Distance from the centre to the surface.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate the volume of a sphere page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate The Volume Of A Sphere, filed under Math. Every number the guide produces comes from substituting into this one line.