Density converter

What it's for

Density says how much a material weighs for a given volume, and it's the number you need every time you go from a litre to a kilo: in the kitchen, when the recipe is in millilitres and the scales in grams; on a building site, to know what a cubic metre of what you're about to load weighs; in a lab, to prepare a solution. Converting between the units is plain arithmetic, but there are many of them and they're mixed across different systems.

The numbers to keep in mind

Water is the reference for everything: 1000 kg/m³ = 1 g/cm³ = 1 kg/L, which is why a litre of water weighs a kilo. Everything else is read against it: ice sits at 917 (which is why it floats), olive oil around 910, honey at 1420, concrete at 2400, aluminium at 2700, steel at 7850, lead at 11,300.

From this comes the most useful practical rule in the kitchen: a litre of oil doesn't weigh a kilo, it weighs about 910 grams. If a recipe says 100 ml of oil and you weigh out 100 grams, you're putting in ten per cent too much.

Density, specific weight and relative density

Three words used as synonyms that aren't. Density is mass divided by volume (kg/m³). Specific weight, strictly speaking, is weight force divided by volume and is measured in newtons per cubic metre: on site it's often used in place of density, and for most sums it makes no difference, but in a physics exercise it does. Relative density is a number with no unit: how many times denser than water that material is, so steel has a relative density of 7.85.

Nearby tools

To move from one volume to another there is Volume converter and for weights Weight converter. In the kitchen, for conversions between spoons, cups and grams, the page is Kitchen measures, and to work out the mass of a chemical formula Molar mass.