Volume Converter
Convert litres, gallons, cups, fluid ounces and more.
Good to know. A UK gallon is about 20% bigger than a US gallon. Same word, different bucket.
How it works
In plain words
Convert the value into litres using the exact size of the unit, then from litres into the target unit.
The formula
result = value × (litres per "from" unit) ÷ (litres per "to" unit) 1 US gal = 3.785411784 L · 1 UK gal = 4.54609 L
Worked example
1 US gallon is exactly 3.785411784 litres, shown rounded as 3.785412 L.
Sources
- NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B Exact conversion factors for US customary units.
- International yard and pound agreement, 1959 1 yard = 0.9144 m and 1 pound = 0.45359237 kg exactly, so 1 inch = 2.54 cm and 1 mile = 1.609344 km.
- Weights and Measures Act 1985, Schedule 1 1 UK gallon = 4.54609 litres.
Sources checked September 29, 2026. 6 automated tests check its answers on every change.
About the volume converter
Volume conversions have one big trap: the US and the UK use units with the same names but different sizes. A UK (imperial) gallon is 4.546 litres, about 20% more than a US gallon at 3.785 litres. A UK pint is 568 ml; a US pint is 473 ml. Even the fluid ounce differs slightly: 29.57 ml in the US and 28.41 ml in the UK.
So always check which system a recipe, fuel figure or product label uses. American recipes and products use US units. Older British recipes and pub pints use imperial units. This converter labels every unit with its country so there is no guessing.
The metric side is simpler. A litre is 1,000 millilitres, and a cubic metre is 1,000 litres. One millilitre is the same as one cubic centimetre, and a litre of water weighs almost exactly a kilogram.
Kitchen measures like cups and spoons are included in their US definitions. Many other countries use a 250 ml metric cup and a 15 ml tablespoon (20 ml in Australia), which are close but not identical. To convert cups of flour or sugar into grams, use the cooking converter, which accounts for the ingredient.
The table below the result shows your value in every unit.
Questions people ask
How many litres are in a gallon?
3.785 litres in a US gallon, and 4.546 litres in a UK (imperial) gallon.
How many ml are in a fluid ounce?
29.57 ml in a US fluid ounce, 28.41 ml in a UK fluid ounce.
How many ml is a cup?
A US cup is 236.6 ml. A metric cup, used in many other countries, is 250 ml.
Is a UK pint bigger than a US pint?
Yes. A UK pint is 568 ml and a US pint is 473 ml.