How the conversion works
Every unit on this page is defined in litres, so converting is a matter of exact factors. The imperial gallon has been defined as exactly 4.54609 litres since 1985, and the UK pint is an eighth of it: 568.26125 ml. The US gallon is an older definition, 231 cubic inches, which works out at exactly 3.785411784 litres. A cubic metre is exactly 1,000 litres, and a millilitre is one thousandth of a litre.
The tool converts your value into litres first, then back out into every other unit, rounding only at the moment of display (to six significant figures), so you can chain conversions without drift.
The UK versus US trap
British and American volume units share names but not sizes, and the differences run in opposite directions, which catches almost everyone. The UK gallon and pint are bigger than their US cousins, but the UK fluid ounce is smaller than the US one:
- UK pint = 568.26 ml, US pint = 473.18 ml (the UK pint is 20% bigger)
- UK gallon = 4.54609 L, US gallon = 3.7854 L (again about 20% bigger)
- UK fluid ounce = 28.41 ml, US fluid ounce = 29.57 ml (the US ounce is slightly bigger)
- A UK pint holds 20 UK fl oz, a US pint holds only 16 US fl oz
That last line is the key to the puzzle: the American pint is smaller because it contains fewer ounces, even though each of its ounces is a touch larger. So when an American recipe says a cup (8 US fl oz, about 237 ml) or a pint, do not reach for a British pint glass. The same trap sits inside fuel economy figures: American mpg numbers use the smaller gallon, so a US-quoted 33 mpg is roughly a UK 40 mpg.
Worked examples
Where you meet each unit
Britain's volume units split by product. Milk and beer keep the pint: draught beer and cider must legally be sold in pints, and doorstep milk still comes in pint bottles, while supermarket milk is labelled in both. Petrol and diesel switched to litres in the 1980s, but drivers still talk in miles per gallon, which is why the gallon refuses to die. Soft drinks, wine and spirits are fully metric (a wine bottle is 750 ml, about 1.32 UK pints), and your water bill arrives in cubic metres, 1,000 litres at a time.
American recipes are the other big source of conversions: cups, US fluid ounces and US pints all need shrinking or growing before a British measuring jug tells the truth. For dry ingredients measured in cups, weight is more reliable than volume, and our cups to grams converter handles the common baking ingredients directly. For quick pint conversions the litres to pints converter is a simpler two-way version of this page, the mpg converter untangles UK and US fuel economy, and the fuel cost calculator turns litres and mpg into money for a real journey.
Frequently asked questions
How many millilitres are in a UK pint?
568.26 ml, or exactly 568.26125 ml. The UK pint is one eighth of the imperial gallon, which is defined as exactly 4.54609 litres. A US pint is smaller at about 473.18 ml, which is why American pint glasses hold noticeably less beer.
What is the difference between a UK gallon and a US gallon?
The UK (imperial) gallon is exactly 4.54609 litres, while the US gallon is exactly 3.785411784 litres, so the UK gallon is about 20 percent bigger. This matters for fuel economy: a car doing 40 miles per UK gallon would only score about 33.3 miles per US gallon on the same journey.
Are UK and US fluid ounces the same?
No, and the difference runs the opposite way to pints. A UK fluid ounce is about 28.41 ml while a US fluid ounce is about 29.57 ml, so the US ounce is slightly bigger even though the US pint is smaller. That works because a UK pint holds 20 UK fluid ounces but a US pint holds only 16 US fluid ounces.
How many litres are in a gallon of petrol?
UK forecourts have sold fuel in litres since the 1980s, but mpg survived, so the useful factor is 4.54609 litres per UK gallon. A 50 litre tank is about 11 UK gallons. If you are reading an American source, its gallon is 3.785 litres, so a 50 litre tank is about 13.2 US gallons.
How many litres are in a cubic metre?
Exactly 1,000 litres, which is why water meters bill in cubic metres. One cubic metre is about 12 and a half baths at 80 litres each, or roughly 1,760 UK pints. Going the other way, a litre is exactly 1,000 cubic centimetres.