Bulk density is the weight of dry soil per unit volume of soil, typically expressed as grams per cubic centimeter (g/cm3) . It is an indicator of soil compaction and affects soil porosity, aeration, rooting depth, available water capacity, and the availability of nutrients for plant use. Bulk density is related to the mineral and organic composition of soil and to soil structure. The bulk density of undisturbed soils ranges from about 1.0 to 1.4 g/cm3, being higher for sands and with increased depth in the soil profile. Sandy soils usually have higher bulk densities (1.3–1.7 g/cm3) than fine silts and clays (1.1 – 1.6 g/cm3) because they have larger, but fewer, pore spaces. The critical value of bulk density for restricting root growth varies with soil type, but in general, bulk densities greater than 1.6 g/cm3 tend to restrict root growth. To calculate bulk density, the dry weight of soil is divided by the total soil volume. Bulk density is usually expressed in megagrams per cubic meter (Mg/m3), but the numerically equivalent units of g/cm3 and t/m3 are also used.