When you wnt the volume of an object you simply multiply the objects width x height x lenghth. But how do you get, let's say, a rocks volume? Its definitely not going to be easy to get a correct answer. Well, this rock is called an irregular object. The way you measure this object's volume is by getting a marked object that can contain luiquid, such as a beaker graduated cylinder or a flask.You then fill it up with water to an even increment, and put the irregular object in there. The water is going to arise. However much it rose, that is your volume. You always write cm3 ( 3 as in cubed ) or cubic centimeters to show that you are writing down the object's volume. That's how you get an irregular object's voume.