Gallons, Quarts, Pints and Cups — US and UK Liquid Measurements Explained

The ladder: 1 gallon = 4 quarts = 8 pints = 16 cups

US liquid measures halve their way down from the gallon. One gallon is 4 quarts, one quart is 2 pints, one pint is 2 cups, and one cup is 8 US fluid ounces. Multiply along the ladder and you get the figures most homework and recipe questions ask for: 1 gallon = 16 cups = 128 fl oz, and 1 quart = 4 cups = 32 fl oz.

Every step is a whole number, so you never need a calculator for the US units themselves. You only need decimals when you cross into metric: one US gallon is exactly 3.785411784 liters, which makes a quart 0.946 L, a pint 473.2 mL and a cup 236.6 mL.

The British (imperial) system uses the same names but different sizes, and that is where most conversion mistakes come from. The chart below puts both side by side.

Reading the chart

The US and imperial columns are both exact: the US gallon is defined as 231 cubic inches (3.785411784 L) and the imperial gallon as exactly 4.54609 L. Every smaller unit is a fixed fraction of its gallon, so the whole column follows from that one number.

Notice the fluid ounce row. An imperial fluid ounce (28.41 mL) is actually slightly smaller than a US one (29.57 mL), yet an imperial pint is larger, because the imperial pint holds 20 fluid ounces and the US pint holds only 16.

Worked problems: quarts to cups

Problem: a recipe uses 4.5 quarts of vegetable broth. How many cups is that? Each quart is 4 cups, so 4.5 × 4 = 18 cups. In metric it is 4.5 × 0.946353 = 4.26 liters, a little more than four 1-liter cartons.

Problem: a soup recipe makes 3 quarts and you want to store it in 2-cup containers. 3 quarts = 12 cups, and 12 ÷ 2 = 6 containers.

Problem: you need 10 cups of stock and the cartons are 1 quart each. 10 cups ÷ 4 = 2.5 quarts, so buy 3 cartons and expect 2 cups left over.

Going the other way, divide cups by 4 to get quarts and by 16 to get gallons. 6 cups = 1.5 quarts = 0.375 gallon. If the numbers do not divide evenly, keep the remainder in cups: 7 cups is 1 quart and 3 cups.

Fluid ounces to cups

Divide US fluid ounces by 8. A 34 oz bottle holds 34 ÷ 8 = 4.25 cups. A 6 oz pour is 0.75 cup. A 64 oz jug is 8 cups, or half a gallon.

This only works for fluid ounces, which measure volume. A recipe that lists 6 oz of flour or chocolate means weight, and a cup of flour weighs only about 4.25 oz. For dry ingredients, use a scale or our ingredient-by-ingredient grams to cups tables in the kitchen section.

US gallons vs UK gallons to liters

An imperial gallon is 1.20095 US gallons, so it is about 20% bigger. 5 US gallons = 18.93 L; 5 UK gallons = 22.73 L. 10 US gallons = 37.85 L; 10 UK gallons = 45.46 L. The same 20% gap applies at every level: a UK pint (568 mL) is 1.2 US pints (473 mL).

Which one does your number use? Anything from the United States (recipes, product labels, US tank and aquarium sizes) uses US gallons. Older British recipes, UK pub pints and UK fuel-economy figures use imperial. Canada and Australia moved to liters for most purposes, but older Canadian sources may still quote imperial gallons.

If you are not sure, convert both ways and sanity-check the result against something you know: a standard US milk jug is 1 US gallon, about 3.8 L.

Pints: the beer glass and the recipe

A US pint is 2 cups (16 fl oz, 473 mL). A UK pint is 568 mL, which is 2.4 US cups. So 0.75 US pint is 1.5 cups, while 0.75 UK pint is 426 mL, or 1.8 US cups.

If a British recipe calls for 1 pint of milk and you measure 2 US cups, you will be about 95 mL short, which is enough to change a batter or custard. Measure 2 1/3 to 2 1/2 US cups, or simply use 570 mL.

Cups are not the same everywhere either

The US customary cup is 236.6 mL. US nutrition labels round it to 240 mL. Australia, New Zealand, Canada and South Africa use a 250 mL metric cup, which is 1.057 US cups. The old British imperial cup was 10 imperial fl oz, about 284 mL, and still turns up in vintage recipes.

For most cooking a 5% difference does not matter. For baking, where a cup of liquid hydrates a fixed amount of flour, it can: 4 metric cups is 1,000 mL, but 4 US cups is only 946 mL.

Dry quarts and pints

The US also has a separate dry pint and dry quart for things like berries sold by volume. A dry quart is 1.101 L, about 16% more than a liquid quart. You will mostly see it on farm-stand fruit boxes; recipes and drinks always mean the liquid quart.

Gallons in fuel economy

Because the gallons differ, so do miles per gallon. A car rated 30 mpg in the US would read about 36 mpg in the UK for exactly the same fuel use, since each UK gallon holds 20% more. In liters per 100 km, 30 US mpg is 7.84 L/100 km. Our fuel economy converter handles US mpg, UK mpg, L/100 km and km/L.

Quick mental shortcuts

A liter is just over a quart (1.057 qt), so 2 L is roughly 2 quarts plus half a cup (8.45 US cups in total). A gallon is just under 4 liters. A cup is just under a quarter liter. A US gallon of water weighs about 8.33 lb; an imperial gallon of water weighs about 10.0 lb, which is how the imperial gallon was originally defined.

When precision matters, for medication, chemicals or scaling a commercial recipe, use the exact factors in the chart or the converters linked on this page instead of the shortcuts.