Formula and example
How it is calculated
V=4πr³/3; S=4πr²; d=2r; great-circle area=πr².
Worked example
For radius 3 cm, the volume is 36π ≈ 113.0973 cm³ and the surface area is 36π ≈ 113.0973 cm². These equal numbers have different units.
Things to check
- The model describes a complete geometrical sphere. A hollow sphere also needs an inner radius.
- Doubling the radius multiplies the surface area by four and the volume by eight.
Frequently asked questions
Why is the circle area different from the sphere surface?
The circle is a flat cross-section through the centre. The entire sphere surface is four times this great-circle area.