Yes, just the measure the volume of the container it is in.
Explanation:
Solid state : It is a state in which the particles are closely packed and does not have any space between them.This state has a definite shape and volume.
Liquid state : It is a state in which the particles are present in random and irregular pattern. The particles are closely arranged but they can move from one place to another. This state has a definite volume but does not have a fixed shape.
Gaseous state : It is a state in which the particles are loosely arranged and have a lot of space between them.This state has indefinite volume as well as shape. They occupy whole of the container in which they are put.
Thus the the volume of a gas can be measured by measuring the volume of the container it is in.
Hope this helps you out!
