Using the relationship between density, mass and volume
You learned in science class that density is the amount of matter in a given volume. Density is a characteristic property of matter, which means that density can be used to identify a sample of matter and the size of the sample will not change the result. Density is determined by dividing the mass of a substance by the volume occupied by that mass.
So, if you know the volume and density of an object, you can find the mass by simply rearranging the above equation.