Volume Converter

Details

About this tool

Converts between litres, millilitres, cubic metres, gallons, pints, cups, fluid ounces and the rest - including the American and British units that share a name and are not the same size.

That last point is the reason this converter needs care. A US gallon is 3.785 litres and an imperial gallon is 4.546 - a 20 per cent difference, which turns fuel consumption figures quoted in miles per gallon into two incompatible numbers. Pints diverge the same way: 473 ml in the United States, 568 ml in Britain and Ireland. Both variants are listed separately, because a recipe or a spec sheet almost never says which it means.

Fluid ounces are the strangest case, because the American one is the larger. A US fluid ounce is 29.57 ml, an imperial one 28.41 ml - the opposite direction from gallons and pints, since a US gallon holds 128 fl oz and an imperial gallon 160. Working from the gallon ratio therefore gives the wrong answer for ounces.

For cooking, the cups matter most: a Polish szklanka and a metric cup are 250 ml, a US customary cup is 236.6 ml and a US legal cup is 240 ml. Across a multi-cup recipe those differences add up to a noticeable amount, especially in baking.

A note on what volume cannot tell you: converting litres to kilograms needs a density and is a different question. A litre of water is a kilogram, a litre of oil is 0.92 and a litre of flour barely half - the mass-to-volume calculator handles that properly rather than assuming water.

Good to know

Questions people actually ask

Is a US gallon the same as an imperial gallon?

No - 3.785 litres against 4.546, a difference of 20 per cent. It is why fuel economy in miles per gallon means two different things depending on which side of the Atlantic the figure came from, and why 40 mpg US is a worse result than 40 mpg imperial.

Why is a US fluid ounce bigger than an imperial one?

Because the gallons are divided differently: a US gallon holds 128 fluid ounces and an imperial gallon 160. So although the US gallon is smaller, its ounce is larger - 29.57 ml against 28.41. Scaling from the gallon ratio gives the wrong answer for ounces, which catches people out.

How big is a cup?

It depends which one. A Polish szklanka and a metric cup are 250 ml, a US customary cup is 236.6 ml, and a US legal cup used on nutrition labels is 240 ml. They are listed separately because recipes rarely specify, and the difference compounds across several cups.

How many litres is a cubic metre?

Exactly 1000, by definition - a litre is a cubic decimetre. That makes metric volume the easy part: every step is a factor of ten, and a cubic centimetre is a millilitre exactly.

How do I convert litres to kilograms?

You cannot, without knowing what the liquid is. Volume and mass are connected only by density: a litre of water is a kilogram, of olive oil 0.92 kg, of honey 1.42 kg. The mass-to-volume calculator does this properly with a density per substance rather than assuming water.