Density Calculator
Density from mass and volume, in kg/m³ and g/cm³, with whether it floats in water.
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Your details
Result
- Density
- 1,000 kg/m³
- In g/cm³
- 1 g/cm³
- Relative to water
- 1×
- In fresh water it would
- Stay suspended
The unit most materials are quoted in
Also called specific gravity
Water is 1000 kg/m³ at 4 °C
1 kg in 0.001 m³…
ρ = m ÷ V
1 ÷ 0.001
ρ = 1,000 kg/m³
Formula — written step by step
1 kg in 1 litre…
ρ = m ÷ V
V = 1 litre = 0.001 m³
1 ÷ 0.001
ρ = 1000 kg/m³
ρ is density, m mass and V volume. A thousand kilograms per cubic metre is the density of fresh water, which is where the kilogram was originally defined from — one litre of water, one kilogram.
A worked example
Is the crown really gold?
- Mass
- 1.2 kg
- Volume displaced
- 77 cm³
- V = 77 cm³ = 0.000077 m³
- ρ = 1.2 ÷ 0.000077
- ρ = 15,584 kg/m³
- Pure gold is 19,300 kg/m³
Not pure gold — about 15,600 kg/m³
This is Archimedes’ problem, and the method still works. Density is an intensive property: it does not depend on how much you have, so a small sample identifies a material as reliably as a large one. The shortfall here is consistent with gold alloyed with a lighter metal such as silver.
How to use this calculator
- Enter the mass and pick its unit.
- Enter the volume and pick its unit. For an irregular object, measure the water it displaces.
- Read the density in kg/m³, or in g/cm³, which is the unit most reference tables use.
- The relative-to-water row is the specific gravity, and decides whether the object floats.
Mass per unit volume
Density is mass divided by volume. It answers how tightly matter is packed, and it is an intensive property: a gram of gold and a tonne of gold have the same density, which is what makes it useful for identifying materials.
The SI unit is kilograms per cubic metre, though grams per cubic centimetre is more common in reference tables. The conversion is simply a factor of a thousand — water is 1000 kg/m³ and 1.00 g/cm³.
Floating and sinking
An object floats when its average density is less than the fluid it sits in. That word "average" is doing the work: a steel ship floats because the hull encloses a great deal of air, so the vessel as a whole is less dense than water even though steel is nearly eight times denser.
Archimedes’ principle gives the mechanism. A floating object displaces its own weight in fluid; a sinking one displaces its own volume. The ratio shown above tells you which happens and, for a floating object, what fraction sits below the surface — ice at 0.917 floats with about 92% submerged.
Density is not fixed
Density changes with temperature and pressure. Most materials expand when heated and so become less dense, which is what drives convection: warm air rises because it is lighter than the cool air around it.
Water is the important exception. It is densest at about 4 °C, not at its freezing point, so ice floats and lakes freeze from the top down. Gases are far more sensitive again — their density depends directly on pressure and temperature, which is what the ideal gas law describes.
Formula & methodology
What this calculator assumes
- Density varies with temperature and, for gases, strongly with pressure. Quoted values are for ordinary room conditions unless stated.
- Water is taken as 1000 kg/m³, its value near 4 °C. It is slightly less dense at room temperature.
- Whether an object floats depends on its average density including any enclosed air, which is why a steel ship floats.
Sources
- Lide (ed.), CRC Handbook of Chemistry and Physics, 97th edition, CRC Press, 2016 — densities of common materials.
Densities of common materials
| Material | kg/m³ | g/cm³ |
|---|---|---|
| Cork | 240 | 0.24 |
| Ice | 917 | 0.917 |
| Fresh water (4 °C) | 1,000 | 1.00 |
| Sea water | 1,025 | 1.025 |
| Concrete | 2,400 | 2.40 |
| Aluminium | 2,700 | 2.70 |
| Steel | 7,850 | 7.85 |
| Lead | 11,340 | 11.34 |
| Gold | 19,300 | 19.30 |
Ice is less dense than water, which is why it floats — and why water pipes burst when they freeze. Very few substances expand on freezing, and life on Earth depends heavily on this one doing so.
Frequently asked questions
How do I find the volume of an irregular object?
Submerge it and measure the water displaced. The volume of water pushed aside equals the volume of the object, which is the observation Archimedes is remembered for.
What is specific gravity?
Density relative to water — the ratio shown above. It has no units, and anything below 1 floats in fresh water.
Why does ice float?
Water expands as it freezes, so ice is about 8% less dense than liquid water. Nearly all other substances contract on freezing and their solid form sinks.
Does density change with temperature?
Yes. Most substances become less dense as they warm. The effect is small for solids and liquids over ordinary ranges, and large for gases.