Calculate the volume of a cylinder

The volume is how much space the cylinder takes up. The radius $r$ is the distance from the middle of the cylinder's round base out to its edge, and the height $h$ is the distance from the base to the top.

The formula is:

$$V = \pi \cdot r^2 \cdot h$$

You first work out the area of the round base, which is $\pi \cdot r^2$, and then multiply it by the height. Think of the cylinder as a stack of identical circles: the base area tells you how big each circle is, and the height tells you how tall the stack is.