Volume Converter

A volume converter changes litres into gallons, millilitres into pints and cubic metres into either — but the important thing it does is keep the two gallons apart. A US gallon is 3.785411784 litres and an imperial gallon is 4.54609 litres, about 20% larger. A recipe, a fuel figure or a tank capacity converted with the wrong gallon is wrong by a fifth, and nothing in the number itself reveals the mistake. Both are offered here by name, along with US and imperial pints, which differ for the same reason. Everything runs in your browser.

How to use it

1. Choose the unit you have — note that US and imperial units are listed separately and never mixed.
2. Type the amount, and the answer appears as you type.
3. Everything converts through litres, so millilitres to gallons is a single exact step.
4. If a source does not say which gallon it means, American recipes and American fuel figures are US gallons; British and older Commonwealth sources are usually imperial.

Examples

• 1 US gallon = 3.785411784 litres.
• 1 imperial gallon = 4.54609 litres.
• 1 litre = 33.814 US fluid ounces.
• 1 cubic metre = 1,000 litres.

Frequently asked questions

How many litres are in a gallon?

It depends which gallon, and the difference is large. A US gallon is 3.785411784 litres; an imperial gallon, still used in the United Kingdom and some Commonwealth countries, is 4.54609 litres. That is a gap of about 20%. Both figures are exact definitions rather than measurements. This is why fuel economy figures are so often misquoted between countries: the same car quoted in miles per gallon looks about 20% more efficient in imperial terms than in US terms, with no change to the car.

What is the difference between a US gallon and an imperial gallon?

They come from different definitions and were never the same. The US gallon inherits the old English wine gallon of 231 cubic inches, fixed before American independence and never revised. The imperial gallon was defined afresh in Britain in 1824 as the volume of ten pounds of water, which came out at 4.54609 litres. So the US kept the older measure and Britain replaced it, leaving two units with one name — 3.785 litres against 4.546. The same split runs through pints and fluid ounces, which is why this page lists them separately rather than offering a single generic pint.

How many millilitres are in a pint?

A US pint is 473.176 millilitres and an imperial pint is 568.261 millilitres — so a pint of beer in London is noticeably larger than one in New York. As with gallons, both are listed here by name. The rough conversions people carry around reflect the split: British sources say a pint is a bit over half a litre, American sources say slightly under. Both are right about their own pint.

How many cubic metres are in a litre?

A litre is one thousandth of a cubic metre, so there are 1,000 litres in a cubic metre. A litre is by definition a cube 10 centimetres on each side, and because a cubic metre is a cube 100 centimetres on each side, it holds ten of those in each direction — 10 x 10 x 10 = 1,000. Cubic metres are the unit for anything large: water tanks, concrete, shipping volume and gas meters.

Which gallon should I use?

Match the source, not your location. If you are converting an American recipe, a US car's fuel economy or a figure from a US datasheet, use the US gallon. If it comes from a British source, an older Commonwealth document or a UK fuel figure, use the imperial gallon. When the source genuinely does not say, the country of origin is the best guide, and a sanity check helps: a typical car fuel tank is around 50 litres, so a figure that converts to 20 gallons is plausible and one that converts to 60 is not.