In one sense, the ideas of volume and capacity are inter-changeable because they both deal with three dimensional space, but in another sense they are different.
• To speak of capacity you must have a container; we speak of the capacity of something. Capacity deals with the quantity of fluid (or other material) that can fit into a container. For example, we can think of the capacity of a tumbler of water, or a carton of milk.
• Volume does not require a container, but deals with the amount of 3D space that the object takes up.
• the empty tumbler is made of glass and the volume is that of the glass.
• the glass full of water has the volume of both materials.
• the cardboard milk carton when empty can be crushed to take up far less volume.
In order to calculate the volume of an object you need to use a formula. It depends which shape or object you are dealing with as to what formula you will need to use. Watch the following YouTube clip to learn a little more.