The volume of a cylinder is:pi( 3.14) x Radius squared time height.Example:What is the volume of a cylinder with a radius of 7cm and a height of 10cm? 3.14 x 49 (7x7)= 153.86 x 10= 1,538.6
You don't need a formula, which is lucky, because there isn't any.
All you have to know is the volume of the container it's in.
Gas always expands to fill the entire volume of the container.