Density Calculator

How to use the density calculator

1. Choose what you want to find: density, mass or volume.
2. Enter the two values you know and pick a unit for each. Units can be mixed, for example grams with cubic inches.
3. Pick the unit you want the answer in. The result is also shown in kg/m³, g/cm³, lb/ft³ and lb/gal, with specific gravity and the nearest match in the table below.

Density formula

Density (ρ, the Greek letter rho) is mass per unit volume: m is the mass of the object or sample and V is the space it occupies. The SI unit is the kilogram per cubic meter. Because 1 g/cm³ is exactly 1,000 kg/m³, a value in g/cm³ (the same as g/mL or kg/L) converts to kg/m³ by multiplying by 1,000. In US units, 1 g/cm³ equals 62.43 lb/ft³ or 8.345 lb per US gallon. Specific gravity is density divided by the density of water at 4 °C, so it has no unit and is numerically almost the same as the density in g/cm³.

Worked examples

• A metal block: a block with a mass of 540 g and a volume of 200 cm³ has a density of 540 ÷ 200 = 2.7 g/cm³, which is 2,700 kg/m³ or 168.6 lb/ft³. The nearest entry in the table is aluminum, a sensible guess for a light, silvery metal, but density alone can't prove what a material is.
• A bucket of liquid: 5 US gallons of liquid with a mass of 41.7 lb has a density of 41.7 ÷ 5 = 8.34 lb/gal, or 999 kg/m³. Its specific gravity is 0.999, so it is very close to water.

Densities of common substances

Values for elements come from the CRC Handbook of Chemistry and Physics as published in the Royal Society of Chemistry periodic table (solids at room temperature, mercury at 25 °C). Ethanol and glycerol are CRC values at 20 °C and ice is at 0 °C. Water is calculated with the Tanaka et al. (2001) equation recommended for metrology. Plastics, glass and concrete are nominal values from NIST, and real products vary by grade and porosity. Air is the standard-atmosphere value at sea level.

Density of water by temperature

Water is densest at about 4 °C and expands as it warms, so a liter of water has a mass of 999.97 g at 4 °C but 998.21 g at 20 °C. Values below are for pure, air-free water at standard atmospheric pressure, from the Tanaka equation (valid from 0 to 40 °C).

Measuring density in practice

• Irregular objects: weigh the object, then lower it into a graduated cylinder of water. The rise in water level is its volume (Archimedes' method). Tie a thin thread to objects that float and push them just under the surface.
• Liquids: weigh an empty container, fill it to a known volume mark and weigh it again. The difference is the mass of the liquid.
• Keep the temperature in mind. Liquids and gases change density with temperature, gases strongly with pressure as well. Always note the conditions next to a measured density.
• Bulk versus solid density: sand, gravel, soil and powders contain air gaps, so a bucketful is much less dense than the solid grains. Use bulk density for ordering loose materials.
• Check the units: most mistakes come from mixing liters with cubic meters or pounds with ounces. This calculator converts every input to SI units before dividing.

To get mass from a density and the size of an object, use the mass calculator. For the force an object exerts on a scale here or on another planet, see the weight calculator. The volume calculator finds the volume of common solids.