Density is the mass per unit volume of a substance. The formula for density is:

density = mass/volume.

The unit for mass is kilograms (kg)/grams (g) and volume in centimetres cubed (cm^{3}) or metres cubed (m^{3}).

Example 1. A stone of mass 20 kg with volume 4 cm^{3} calculate its density.

density = mass/volume = 20kg/4cm3 = 5kg/cm3