Density Converter — How to Convert Density Units
Density is a physical property that describes mass per unit volume. It is denoted by the Greek letter ρ (rho). Formula: ρ = m / V, where m is mass and V is volume. The SI unit is kilogram per cubic metre (kg/m³). Our density converter allows instant conversion between 11 different units.
kg/m³ and g/cm³ — the Primary Units
Kilogram per cubic metre (kg/m³) is the SI standard. Gram per cubic centimetre (g/cm³) is the most practical unit because water has a density of exactly 1 g/cm³. The conversion is straightforward: g/cm³ = kg/m³ ÷ 1,000. The units g/mL, kg/L and t/m³ all give the same numerical value as g/cm³.
Common Material Densities
Water (4 °C) — 1,000 kg/m³, the reference standard. Air — just 1.2 kg/m³. Aluminium — 2,700 kg/m³ (a lightweight metal). Iron and steel — 7,800–7,900 kg/m³. Gold — 19,320 kg/m³. Mercury — 13,546 kg/m³ (the only metal that is liquid at room temperature). Gasoline — 750 kg/m³ (floats on water). Ice — 917 kg/m³ (lighter than water, which is why it floats).
Imperial Density Units
In the US and UK, density is commonly expressed as lb/ft³ (pound per cubic foot) and lb/in³ (pound per cubic inch). Water ≈ 62.43 lb/ft³. Also common is lb/gal — pound per gallon, noting that the US and UK gallons differ: US gallon = 3.785 L, UK gallon = 4.546 L.
Practical Applications
Knowing density is essential for calculating material mass in construction (concrete, steel), determining fuel quality (gasoline, diesel), dairy product quality control, pharmaceutical calculations (mg/mL), and determining buoyancy (comparing with the density of water).