Density Calculator
Calculate density from mass and volume, or mass or volume from density, in kg/m³, g/cm³ or lb/ft³. Includes a material table and the water displacement method.
The interactive tool loads here when JavaScript runs.
About this toolWhat is the Density Calculator?
This density calculator solves ρ = m ÷ V for whichever of density, mass and volume you are missing. Enter the two you know in any mix of units (grams and cubic centimetres, pounds and gallons, tonnes and cubic metres) and the third appears with its conversions to kg/m³, g/cm³ and lb/ft³, plus the specific gravity and whether the material floats in water.
When you solve for mass or volume, you can pick a material from the built-in table of about 35 metals, liquids, gases, woods, plastics and building materials instead of typing a density. That turns the tool into a quick "how much does 2 litres of steel weigh" or "how many litres is a kilo of olive oil" calculator. When you solve for density, it names the closest materials in the table.
A second tab finds the density of an irregular object by weighing it twice, once in air and once hanging under water, the method Archimedes is said to have used on King Hiero's crown. The water density is corrected for temperature with the CIPM formula.
- Solve for density, mass or volume
- Eight density units including g/cm³, lb/ft³ and lb/gal
- Table of about 35 materials with closest-match lookup
- Archimedes method with temperature-corrected water density
- Specific gravity and float or sink check
How to use the Density Calculator
- On the first tab, choose what to solve for: density, mass or volume.
- Enter the two known values and pick their units. When solving for mass or volume you can choose a material to fill in the density.
- Read the result in your chosen unit, with conversions, the specific gravity and the closest materials.
- To measure an irregular object, open the Archimedes tab, enter the mass in air and the apparent mass fully under water, and the water temperature.
- Use the Material densities tab to browse the reference table by group.
Worked examples
Identify a metal block
Input
500 g, 185 cm³
Output
2.703 g/cm³ (2,703 kg/m³); closest: aluminium
Specific gravity 2.70, so it sinks. Aluminium is 2.70 g/cm³.
Mass of a steel part
Input
Solve for mass; carbon steel, 2 L
Output
15.7 kg (34.6 lb)
7,850 kg/m³ × 0.002 m³. The same volume of aluminium would be 5.4 kg.
Testing a gold bar by weighing it in water
Input
100 g in air, 94.82 g under water at 20 °C
Output
19.27 g/cm³; closest: gold
The 5.18 g loss means 5.189 cm³ of water was displaced. A gold-plated tungsten bar would also pass (tungsten is 19.25 g/cm³), so this test catches lead or silver cores, not tungsten.
Volume of a kilogram of liquid
Input
Solve for volume; olive oil, 1 kg
Output
1.093 L
Oil is lighter than water, so a kilogram takes up more than a litre.
Background and insight
Density is mass per unit volume. The SI unit is kg/m³; chemists often use g/cm³, which equals g/mL and kg/L and is 1,000 times the SI number. Water at its densest (about 4 °C) is 999.97 kg/m³, very nearly 1 g/cm³, which is no accident: the gram was originally defined as the mass of a cubic centimetre of water. Specific gravity, or relative density, is a material's density divided by that of water, so it has no units.
Densities change with temperature and, for gases, strongly with pressure. Water is 998.2 kg/m³ at 20 °C and 997.0 at 25 °C (Tanaka et al., 2001, the formula adopted by the International Committee for Weights and Measures). Air is about 1.204 kg/m³ at 20 °C and 1 atm but less than half that at the top of Everest. The table lists values at about 20 °C; alloys, woods, plastics and fuels vary by grade and are marked as typical.
Hydrostatic weighing uses Archimedes' principle: an object under a fluid is pushed up by a force equal to the weight of fluid it displaces. The loss in apparent mass equals the mass of water displaced, which divided by the water density gives the object's volume. Gold at 19.3 g/cm³ is far denser than silver (10.49) or lead (11.34), which is why the method can expose a plated or alloyed fake.
Common use cases
Science classes
Work density problems in any units and check specific gravity and floating or sinking.
Material identification
Measure an unknown object and compare its density with metals, plastics and woods.
Weight estimates
Find the mass of a part, a tank of fuel or a load of concrete from its volume.
Jewellery and bullion checks
Use the two-weighing method to test whether a ring, coin or bar is the metal it claims to be.
Tips and limitations
- Volume is the hardest part to measure. For irregular solids, the Archimedes tab avoids measuring dimensions altogether.
- For liquids, measure at a known temperature; many liquids change density by about 0.1% per 1 to 2 °C.
- Porous materials such as wood, foam and soil have a bulk density (including air spaces) far below their solid density. Use the figure that matches how you measured volume.
- For gases, use the ideal gas law calculator instead: density depends on pressure and temperature, ρ = PM ÷ RT.
- Specific gravity here is relative to water at 4 °C (999.97 kg/m³). Some industries use 15.6 °C (60 °F) as the reference, which shifts the figure by about 0.1%.
Frequently asked questions
What is the formula for density?
Density = mass ÷ volume, ρ = m ÷ V. 500 g in 185 cm³ gives 2.70 g/cm³. Rearranged, mass = density × volume and volume = mass ÷ density.
How do I convert g/cm³ to kg/m³?
Multiply by 1,000. Water is 1 g/cm³ = 1,000 kg/m³ and steel is 7.85 g/cm³ = 7,850 kg/m³. g/cm³, g/mL and kg/L are all the same number.
How do you find the density of an irregular object?
Weigh it in air, then weigh it hanging fully under water. Divide the mass in air by the loss in mass, and multiply by the water density. The Archimedes tab does this and corrects for water temperature.
What is specific gravity?
The density of a material divided by the density of water, so it has no units. Anything with a specific gravity below 1 floats in fresh water; ice at 0.917 floats with about 92% of its volume submerged.
What is the density of water?
999.97 kg/m³ at about 4 °C, its maximum; 998.21 kg/m³ at 20 °C and 997.05 kg/m³ at 25 °C. Seawater is about 1,025 kg/m³ because of the dissolved salt.
Can the water test prove gold is real?
It rules out most fakes, such as plated lead, copper or silver, because their densities are far from 19.3 g/cm³. It cannot catch tungsten, which has almost the same density as gold, so serious buyers also use ultrasonic or X-ray fluorescence testing.
Is there an in-depth guide to the Density Calculator?
Yes. “Density, Mass and Volume: Formula, Units and the Archimedes Test” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
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