What this tool does
This converter handles the five UK volume units in everyday use: millilitres, litres, UK fluid ounces, UK pints, and UK gallons. Select a from-unit and a to-unit, enter a value, and the result updates instantly in your browser. All conversions go through millilitres as a common base.
The units explained
The millilitre (ml) is the SI base unit here — one thousandth of a litre, equal to one cubic centimetre. The litre is 1,000 ml, the standard unit for drinks bottles, fuel, and cooking liquids. The UK fluid ounce, pint, and gallon are all defined relative to each other — 20 fl oz to the pint, 8 pints to the gallon — so once you fix the pint in millilitres, the rest follow exactly.
The pint problem
"A pint" is not one measure — it is at least three, and they don't convert into each other by a tidy ratio. A UK (imperial) pint is 568.26125 ml. A US liquid pint is 473.18 ml — about a sixth smaller (equivalently, the UK pint is 20% larger). A US dry pint, used for produce like berries sold by the box, is 550.61 ml, sitting between the two: 16% bigger than the US liquid pint but still 3% short of the UK pint. Ask for "a pint" in London, Boston, and a New Jersey farm stand and you'd get three different volumes.
The split dates to the Weights and Measures Act 1985 and its predecessors: Britain's 1824 reform redefined the gallon as the volume of exactly 10 lb of water, fixing the 8-pint imperial gallon at its current size. The United States had already fixed its own colonial-era gallon before that reform and never adopted it, so American and British pints have been on separate tracks ever since — and the US kept a second, older dry-measure gallon alongside its liquid one, which is where the dry pint comes from.
Why UK and American recipes clash
The practical fallout shows up in the kitchen. American recipes measure by volume — cups, tablespoons, teaspoons — and a "cup" of flour can vary by up to 20% depending on whether it was scooped and levelled or spooned in loosely, because flour compresses. UK and most European baking sidesteps the whole pint problem for dry ingredients by weighing on a kitchen scale instead: 250 g of flour is 250 g of flour regardless of how it settled in the bag. Liquids are the exception — UK recipes still quote milk, stock, and water in millilitres or pints, so a US recipe's "1 pint of cream" (473 ml) genuinely is less than a UK pint of cream (568 ml), not just a rounding difference.
Fluid ounces differ too
Because the UK and US pints differ, so do their fluid ounces, even though both split a pint into 16 or 20 parts. A UK fluid ounce is exactly 28.4130625 ml (1/20 of a UK pint). A US fluid ounce is 29.57 ml (1/16 of a US liquid pint) — about 4% larger. Substitute one for the other in a cocktail or baking recipe without adjusting and every measure comes out slightly off, and the error compounds across a multi-ingredient recipe.
UK gallon vs US gallon
A UK gallon is 4,546.09 ml; a US gallon is 3,785.41 ml — about a sixth smaller, the same ratio as the pints, since both gallons are just 8 pints of their respective sizes. This matters for fuel economy: a UK mpg figure and a US mpg figure aren't the same distance-per-gallon, so a car rated 40 mpg UK would show roughly 33 mpg on a US scale even with identical fuel consumption.
Worked example
Take 1 UK pint:
1 UK pint × 568.26125 = 568.2613 ml
Each UK pint contains exactly 20 UK fluid ounces and 1/8 of a UK gallon, so the same figure can be re-expressed either way without leaving the UK system. It's only when a recipe, a cocktail menu, or a US website hands you a pint or fluid ounce measure that you need to stop and check which pint they mean.
Common uses
- Pub measures: draught beer and cider are one of the few goods UK law still requires to be sold in imperial units — by the pint, half-pint, or third — under the Weights and Measures Act, so 568 ml is a legal quantity, not a habit.
- Following US recipes: converting American cup and fluid-ounce measures into ml avoids the cup-density trap and the UK/US fluid ounce mismatch in one step.
- Fuel and mpg: UK pump prices are per litre; UK mpg figures use the UK gallon (4,546 ml), so comparing against a US-sourced mpg figure needs a unit check first.
- Medicine: liquid medicines are dosed in ml everywhere, sidestepping the pint problem entirely — no ambiguity across countries.
- Dairy: UK milk is sold in 568 ml (1 pint), 1,136 ml (2 pints), and 2,272 ml (4 pints) bottles — pint-based sizing that predates and survives metrication.
Frequently asked
How many ml in a pint?
Depends which pint. A UK pint is exactly 568.26125 ml. A US liquid pint is 473.18 ml. A US dry pint (used for produce, not drinks) is 550.61 ml. This tool uses UK pints throughout.
How many pints in a gallon?
Exactly 8 pints in a gallon, in both the UK and US systems — but since a UK pint and a US pint aren't the same size, a UK gallon (4,546.09 ml) and a US gallon (3,785.41 ml) aren't either.
Why is a US pint smaller than a UK pint?
Britain's Weights and Measures Act 1824 redefined the gallon (and so the pint) against 10 lb of water, giving the modern imperial sizes. The US had already fixed its own gallon before 1824 and kept it, so the two never lined up. The gap is exactly why an American "pint glass" holds noticeably less than a British one.
Is a UK fluid ounce the same as a US fluid ounce?
No. A UK fluid ounce is 28.4130625 ml; a US fluid ounce is 29.57 ml — about 4% larger. Substituting one for the other in a US cocktail or baking recipe throws every measure off by that margin.