About the Density Converter
This density converter changes a density (mass per unit volume) between metric and US customary units. Pick the unit you have — kg/m³, g/cm³, g/L, lb/ft³, lb/in³ or pounds per US or UK gallon — enter the value, and every other unit is calculated at once, so there is no need to chain conversions.
Engineers and students use it to move between SI data sheets and imperial tables, builders and fabricators to estimate the weight of concrete or steel, and brewers, chemists and fuel handlers to turn a density in g/mL into pounds per gallon. The material table gives typical densities for water, metals, concrete and fuels as a reference point.
All factors come from the exact definitions of the pound (0.45359237 kg), the foot (0.3048 m), the inch (2.54 cm) and the gallon, so the conversions are exact. Real material densities vary with temperature, composition and pressure, so the reference values are typical figures, not specifications.
With the default inputs, the kilograms per cubic meter is 1,000 kg/m³. Change any value above to recalculate instantly.
How to use the density converter
- 1Enter the density value you have.
- 2Choose its unit from the list (kg/m³, g/cm³, lb/ft³, lb/gal and so on).
- 3Read the value in every other unit, plus specific gravity.
- 4Compare against the reference material densities in the table.
Formula and method
Every unit is first converted to the SI base unit, kilograms per cubic meter, then into the target unit. The factors come from exact definitions: 1 g/cm³ = 1,000 kg/m³; 1 lb/ft³ = 0.45359237 kg ÷ 0.028316846592 m³ ≈ 16.0185 kg/m³; 1 lb/US gal ≈ 119.826 kg/m³; 1 lb/in³ ≈ 27,679.9 kg/m³.
Specific gravity is the density divided by the density of water at 4 °C (1,000 kg/m³), so a specific gravity of 7.85 means the material is 7.85 times as heavy as the same volume of water.
- ρ
- Density (mass ÷ volume)
- SG
- Specific gravity = ρ ÷ 1,000 kg/m³
Worked examples
Water: 1 g/cm³
1 g/cm³ is 1,000 kg/m³. Dividing by 16.0185 gives 62.43 lb/ft³, and dividing by 119.826 gives 8.345 lb per US gallon — the familiar "a gallon of water weighs about 8.34 lb".
Structural steel: 7.85 g/cm³
7.85 × 1,000 = 7,850 kg/m³. In US units that is 7,850 ÷ 16.0185 = 490.1 lb/ft³, or 0.284 lb per cubic inch — the figure used for steel weight estimates.
Concrete quoted as 150 lb/ft³
150 × 16.0185 = 2,402.8 kg/m³, which matches the common metric figure of about 2,400 kg/m³ for normal-weight concrete.
Frequently asked questions
How do I convert g/cm³ to kg/m³?+
Multiply by 1,000. One gram per cubic centimeter equals 1,000 kilograms per cubic meter, so aluminum at 2.70 g/cm³ is 2,700 kg/m³.
How do I convert kg/m³ to lb/ft³?+
Divide by 16.0185 (or multiply by 0.062428). For example, water at 1,000 kg/m³ is 1,000 ÷ 16.0185 = 62.43 lb/ft³.
Is g/cm³ the same as g/mL?+
Yes. A cubic centimeter is exactly one milliliter, so g/cm³, g/mL and kg/L are all numerically identical.
How much does a gallon of water weigh?+
A US gallon of water weighs about 8.34 lb at room temperature (8.345 lb at its densest, 4 °C). A UK (imperial) gallon weighs about 10.02 lb.
What is specific gravity?+
Specific gravity is the ratio of a substance's density to the density of water. It has no units: a value above 1 sinks in water, below 1 floats.