Density can be described as the amount of mass per unit volume. It describes how closely together different particles are spaced. It varies significantly from solids to liquids to gases.In terms of calculating it the formula: Density = Mass / Volume is used.In this example Density = 2200 / 4 = 550 Kg/m3It is important to ensure the units are correct. in this case it is Kg divided by m3 so the units would be Kg/m3.