Density Calculator (Mass ÷ Volume, kg/m³, g/cm³, lb/ft³)
Density from mass and volume in kg/m³, g/cm³ and lb/ft³, with specific gravity and whether it floats in water.
Inputs
- Working
- 1000 kg ÷ 1 m³ = 1,000 kg/m³
- In g/cm³ (= kg/L = t/m³)
- 1 g/cm³
- In lb/ft³
- 62.428 lb/ft³
- Specific gravity (vs water at 1,000 kg/m³)
- 1 — neutrally buoyant in water
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What each Density input means
- Mass
- The object's mass in kilograms. Grams ÷ 1,000 are kilograms.
- Volume
- Its volume in cubic metres. A litre is 0.001 m³ and 1 cm³ is 0.000001 m³; for an irregular object, the water it displaces gives the volume.
Density formula
ρ = mass ÷ volume · 1 g/cm³ = 1,000 kg/m³ = 1 kg/L · 1 kg/m³ = 0.06243 lb/ft³ · specific gravity = ρ ÷ 1,000 kg/m³ (water)
Density is mass per unit volume — how much stuff is packed into a given space. In SI units it is kilograms per cubic metre; water is 1,000 kg/m³, which is the same as 1 g/cm³ or 1 kg per litre, and that convenient number is why densities are often quoted as a specific gravity, the ratio to water's. Anything with a specific gravity below 1 floats in water and anything above sinks, which the page states for the value it finds. Enter the mass in kilograms and the volume in cubic metres (a litre is 0.001 m³) and the page gives the density in the three common units with the division shown. Density identifies materials — 2,700 kg/m³ is aluminium, 7,850 steel, 19,300 gold — and is the number behind buoyancy, fuel weights and cargo limits.
Density worked example
1,000 kg in 1 m³: 1,000 ÷ 1 = 1,000 kg/m³ — water, specific gravity 1.000, 62.43 lb/ft³. A 917 kg cubic metre is ice, specific gravity 0.917, which is why only about a tenth of an iceberg shows above the sea (seawater is about 1,025 kg/m³). A 2.7 kg block of aluminium occupying 0.001 m³ (one litre) is 2,700 kg/m³ and sinks.
More Density examples
A litre of ice weighing 0.917 kg: 0.917 ÷ 0.001 = 917 kg/m³, specific gravity 0.917, so it floats with about 92% of its volume under fresh water.
A one-litre block weighing 19.32 kg: 19,320 kg/m³, the density OpenStax lists for gold. A gold-plated tungsten fake comes very close (tungsten is 19,300), which is why density alone cannot always tell them apart.
Where the Density calculator can give the wrong answer
- Volume must be the object's actual volume. A hollow or porous object — a steel ship, a pumice stone — has a bulk density far below its material's, which is the whole reason ships float.
- Density changes with temperature and, for gases, pressure. Water is 1,000 kg/m³ at 4 °C and 958 at 100 °C; air is 1.2 kg/m³ at sea level.
- Units: kilograms and cubic metres. Grams and millilitres give g/mL, which is numerically g/cm³ — divide the kg/m³ figure by 1,000 — and the page shows both.
- Floating or sinking is judged against fresh water. Seawater is about 1,025 kg/m³, so an object of 1,010 kg/m³ sinks in a lake and floats in the sea.
- Volume from external measurements includes surface irregularities; displacement (the water an object pushes aside) is the reliable way to measure it.
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Density reference table
| Substance | Density (kg/m³) | In g/cm³ |
|---|---|---|
| Gasoline | 680 | 0.68 |
| Ice (0 °C) | 917 | 0.917 |
| Fresh water | 1,000 | 1.000 |
| Seawater | 1,025 | 1.025 |
| Aluminium | 2,700 | 2.7 |
| Brass | 8,440 | 8.44 |
| Copper (average) | 8,800 | 8.8 |
| Lead | 11,300 | 11.3 |
| Mercury | 13,600 | 13.6 |
| Gold | 19,320 | 19.32 |
Density FAQ
- Divide the mass by the volume. 500 g in 250 cm³ is 2 g/cm³, or in SI 0.5 kg ÷ 0.00025 m³ = 2,000 kg/m³. Enter kilograms and cubic metres above; the page converts to g/cm³ and lb/ft³.
- 1,000 kg/m³ (1 g/cm³, 1 kg/L, 62.4 lb/ft³) at 4 °C, and very slightly less at room temperature — 997 kg/m³ at 25 °C. It is the reference for specific gravity.
- Compare its density with the liquid's. Below 1,000 kg/m³ it floats in fresh water: wood (500–800), ice (917), oil (900). Above, it sinks: aluminium (2,700), steel (7,850). The page says which for the density it finds.
- Divide by 1,000: 2,700 kg/m³ is 2.7 g/cm³. Going the other way, multiply by 1,000. For lb/ft³, multiply kg/m³ by 0.06243.
- By displacement: note the water level in a measuring jug, submerge the object and read the rise. Each millilitre of rise is 1 cm³, or 0.000001 m³. Archimedes' principle, in OpenStax §11.7, turns the same idea into a way to find density by weighing an object in and out of water.
- The density divided by water's 1,000 kg/m³, so it has no units: aluminium is 2.7 and gasoline 0.68. Below 1 an object floats in fresh water; above 1 it sinks.