The equation for density is ρ = m/V, where ρ is density, m is mass, and V is volume. Density is usually expressed in units of grams per cubic centimeter or kilograms per cubic meter. To calculate density, you need to know the mass and volume of the object. For example, if an object has a mass of 500 kg and a volume of 2.5 cubic meters, the density would be 200 kg/m³. It is important to ensure that the units of mass and volume are compatible when using the density formula to calculate density, mass, or volume.