Bulk density. Bulk density (g/cm3) = Dry soil weight (g) / Soil volume (cm3) Bulk density is usually expressed in megagrams per cubic metre (Mg/m3) but the numerically equivalent units of g/cm3 and t/m3 are also used (1 Mg/m3 = 1 g/cm3 = 1 t/m3) (Cresswell and Hamilton, 2002).