Density Calculator
Calculate density, mass, or volume from any two known values. Supports g/cm³, kg/m³, lb/ft³ with material presets.
Enter two values and click Calculate.
How Does the Formula Work?
The density calculator solves ρ = m/V: density equals mass divided by volume. Give it any two of the three quantities and it returns the third, with every result shown in three units: g/cm³, kg/m³ and lb/ft³ for density, grams, kilograms and pounds for mass, and cubic centimetres, litres and cubic metres for volume. Ten presets fill in the density of water, ethanol and eight common metals.
Mass = Density × Volume
Volume = Mass ÷ Density
Unit Conversions: 1 g/cm³ = 1,000 kg/m³ = 1 kg/L = 62.42796 lb/ft³
1 lb = 0.45359237 kg and 1 ft = 0.3048 m, exactly (NIST SP 811)
Example: 100 g ÷ 50 cm³ = 2 g/cm³ = 2,000 kg/m³
What Is Density?
Density tells you how much mass is packed into a given volume. Water sits close to 1 g/cm³ (1,000 kg/m³), which makes it a convenient yardstick: an object denser than the water around it sinks, and a less dense one floats. A steel ship stays up because its hull encloses a large volume of air, which brings the average density of hull plus air below that of water. Density also moves with temperature. The USGS table lists water at 1 g/cm³ at 4 °C, 0.99987 g/cm³ at 0 °C and 0.99669 g/cm³ at 26.7 °C, so careful work always says at what temperature a density was measured.
Where the Presets Come From
The eight metal presets are the figures printed in the Royal Society of Chemistry periodic table: aluminium 2.70, titanium 4.506, iron 7.87, copper 8.96, silver 10.5, lead 11.3, mercury 13.5336 and gold 19.3 g/cm³. The same table gives osmium 22.5872 g/cm³ and names it the densest element. Ethanol is 0.7893 g/cm³ at 20 °C (PubChem, quoting the CRC Handbook), lighter than water. Because iron is less dense than mercury, a lump of iron floats on mercury.
Worked Examples
A metal sample of 89.6 g that displaces 10 cm³ has a density of 8.96 g/cm³, exactly the copper preset. One kilogram of gold takes up 1,000 ÷ 19.3 ≈ 51.81 cm³. A litre of ethanol weighs 789.3 g, against 1,000 g for a litre of water near 4 °C. And 270 g of aluminium fills 100 cm³.
Specific Gravity
Specific gravity is a substance's density divided by the density of water, so it carries no unit. Taking water as 1 g/cm³, copper has a specific gravity of 8.96 and ethanol of 0.7893. Precise work states the temperature of the sample and of the water, because both densities change with it.
Tips & Recommendations
Water is very close to 1 g/cm³ at 4 °C and slightly less when warmer, which makes it the usual reference.
In water, an object below about 1 g/cm³ floats and one above it sinks.
Pure gold is 19.3 g/cm³. A piece that measures well below that is not pure gold.
In Mass or Volume mode, pick a material and its density fills the first field.
Frequently Asked Questions
What is the formula for density?
Density = Mass ÷ Volume (ρ = m/V). Enter any two values to find the third.
What is water's density?
Close to 1 g/cm³, that is 1,000 kg/m³ or 1 kg/L. USGS lists 1 at 4 °C as the usual rounded figure, says the exact value there is slightly lower (0.9998395 g/ml), and gives 0.99987 at 0 °C and 0.99669 at 26.7 °C.
Why does ice float?
Water takes up more room once it freezes, so ice ends up lighter than the liquid around it; USGS puts ice at roughly nine tenths of the density of water.
What units are supported?
Density: g/cm³, kg/m³, lb/ft³. Mass: g, kg, lb. Volume: cm³, L, m³.
How do I identify an unknown metal?
Measure its mass and volume, calculate the density, then compare it with the metal presets, which come from the Royal Society of Chemistry periodic table.
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Sources
- Royal Society of Chemistry, Periodic Table: densities of aluminium, titanium, iron, copper, silver, lead, mercury, gold and osmium (g cm⁻³)
- PubChem, Ethanol (CID 702): density 0.7893 g/cm³ at 20 °C, from the CRC Handbook of Chemistry and Physics
- USGS Water Science School, Water Density: density of water by temperature, 1 g/cm³ rounded at 4 °C
- NIST SP 811, Guide for the Use of the International System of Units: Appendix B.8 (pound 0.45359237 kg, foot 0.3048 m)