Quick brief

What to know before you calculate

A short read on the assumptions, trade-offs and definitions that shape the answer.

  • Density equals mass divided by volume.
  • The same material can be described with different density units.
  • Mass and volume units must be converted before comparing results.

The density formula

Density describes how much mass sits inside a given volume. The formula is density equals mass divided by volume. Rearranging the formula gives mass equals density multiplied by volume, and volume equals mass divided by density.

Units change the number

A density value can be shown in grams per cubic centimetre, kilograms per cubic metre or other unit pairs. The material has not changed, but the number changes with the units. Always keep the unit attached to the result.

Compare like with like

Before comparing two densities, convert them to the same unit. A value in kilograms per cubic metre should not be compared directly with a value in grams per millilitre unless one is converted first.

Use realistic measurements

A density calculation is only as good as the mass and volume measurements. Irregular shapes, trapped air, temperature and measurement precision can all affect the result. Treat classroom and practical estimates as checks, not perfect constants.

Related calculators

Try the numbers yourself

Open the calculators that match this topic and test the result with your own inputs.

DensityCalculate density, mass or volume when you know the other two values, with unit notes for science and engineering checks.VolumeCalculate volume for a cuboid, cylinder, sphere or cone, with clear units for maths, science and project estimates.Unit ConversionConvert common length, weight, temperature and volume units with instant results.