About Density

Density is mass per unit volume: ρ = m / V. The SI unit is kg/m³; g/cm³ and g/mL are also common for liquids and solids. An object floats in a fluid if its density is lower than the fluid's. Density is temperature-dependent — liquids generally become less dense as they heat up (water is the famous exception near 4 °C).

Common Conversions

  • 1 g/cm³ = 1,000 kg/m³ = 1 g/mL
  • 1 kg/m³ = 0.001 g/cm³
  • 1 lb/ft³ = 16.018 kg/m³
  • 1 lb/in³ = 27,680 kg/m³

Material Densities

  • Air (sea level, 20 °C): 1.204 kg/m³
  • Water (4 °C): 1,000 kg/m³ (1 g/cm³)
  • Aluminium: 2,700 kg/m³
  • Iron/Steel: 7,874 kg/m³
  • Gold: 19,300 kg/m³
  • Osmium (densest element): 22,590 kg/m³