How do I calculate density?

Divide mass by volume. 500 g in 250 cm³ gives 2 g/cm³.

What is the density of water?

1 g/cm³, or 1,000 kg/m³, at 4°C. One litre weighs one kilogram, which makes it a handy reference point.

Water is unusual in expanding as it freezes, so ice is less dense than liquid water at about 0.92 g/cm³ and floats.

How do I find the volume of an irregular object?

Displacement. Submerge it in water and measure the rise; the volume of water displaced equals the volume of the object.

Density Calculator - Mass, Volume and Density

Density Calculator

Density is how much mass is packed into a given volume. Enter any two of mass, volume and density and this calculator returns the third.

Formula

ρ = m ÷ V

ρ = density, m = mass, V = volume
Rearranged: m = ρV and V = m ÷ ρ

500 g in 250 cm³: 500 ÷ 250 = 2 g/cm³

The Formula

Density = Mass ÷ Volume

Rearranged: mass = density × volume, and volume = mass ÷ density.

500 g occupying 250 cm³ gives a density of 2 g/cm³.

The convenient coincidence is water: 1 g/cm³, or 1,000 kg/m³. One litre of water weighs one kilogram, which makes water a useful mental reference for everything else.

Densities Worth Knowing

Air: 0.0012 g/cm³
Water: 1.00 g/cm³
Aluminium: 2.7 g/cm³
Steel: around 7.85 g/cm³
Lead: 11.3 g/cm³
Gold: 19.3 g/cm³

Anything denser than water sinks in it; anything less dense floats. A steel ship floats because its average density, hull and enclosed air together, is below 1 g/cm³.

Density Changes With Temperature

Materials expand when heated, so the same mass occupies more space and density falls. This drives convection: warm air rises because it is less dense than the cool air around it.

Water is the famous exception. It is densest at about 4°C and expands as it freezes, which is why ice floats and why pipes burst in winter.

Quick Reference

Densities at room temperature. Anything under 1 g/cm³ floats on water.
Material	g/cm³	kg/m³
Cork	0.24	240
Petrol	0.75	750
Ice	0.92	920
Water	1.00	1,000
Concrete	2.4	2,400
Aluminium	2.70	2,700
Steel	7.85	7,850
Lead	11.34	11,340
Gold	19.32	19,320

Frequently Asked Questions

How do I calculate density?: Divide mass by volume. 500 g in 250 cm³ gives 2 g/cm³.
What is the density of water?: 1 g/cm³, or 1,000 kg/m³, at 4°C. One litre weighs one kilogram, which makes it a handy reference point.
Why does ice float?: Water is unusual in expanding as it freezes, so ice is less dense than liquid water at about 0.92 g/cm³ and floats.
How do I find the volume of an irregular object?: Displacement. Submerge it in water and measure the rise; the volume of water displaced equals the volume of the object.