US vs Imperial Gallons, Pints, Cups and Spoons
Gallons, pints and fluid ounces are used in both the United States and the United Kingdom, but they are not the same size. The US system descends from older English measures, while the imperial system was a later standardization in Britain.
If you follow a British recipe in the US, read a fuel economy figure from abroad or compare product labels, knowing which unit is meant avoids errors of around 20%. This guide sets the two systems side by side.
The two gallons
A US liquid gallon is 231 cubic inches, which is 3.785 liters. An imperial gallon is 4.546 liters. Dividing one by the other shows the imperial gallon is about 20% larger.
1 imperial gallon = 4.54609 ÷ 3.78541 = 1.2009 US gallons
Both gallons split into 4 quarts and 8 pints. The units below them differ because the imperial pint holds 20 fluid ounces and the US pint only 16, while the imperial fluid ounce is slightly smaller than the US one.
| Unit | US | Imperial |
|---|---|---|
| Gallon | 3.785 L | 4.546 L |
| Quart | 0.946 L | 1.137 L |
| Pint | 473 mL (16 fl oz) | 568 mL (20 fl oz) |
| Fluid ounce | 29.57 mL | 28.41 mL |
| Fluid ounces per gallon | 128 | 160 |
Worked examples
A British recipe asks for 1 pint of milk. An imperial pint is 568 mL. A US customary cup is 236.6 mL, so 568 ÷ 236.6 = 2.4 US cups, not the 2 cups that a US pint would suggest.
A tank is listed as 5 imperial gallons. That is 5 × 4.546 = 22.7 L, which is about 6.0 US gallons. Reading it as 5 US gallons (18.9 L) would understate the capacity by about 3.8 L.
The same ratio explains why a car's miles-per-gallon figure looks about 20% higher in UK terms than in US terms: 30 US mpg is 36 miles per imperial gallon. The article on MPG and liters per 100 km works through it.
Pints of drink
The pint difference is easy to notice with drinks. A British pint of beer is an imperial pint, 568 mL or 20 imperial fluid ounces. In US fluid ounces that is 568.26 ÷ 29.57 = 19.2 fl oz. A US pint is 473 mL, which is 473.18 ÷ 28.41 = 16.7 imperial fluid ounces. A UK pint is therefore about 20% more liquid than a US pint.
Packaged drinks are usually labelled in milliliters or in fluid ounces of the local system, so a quick check of the milliliter figure is the safest way to compare two products.
Cups and spoons
Even inside the US, the cup is not a single size. Recipes and labels use several:
- US customary cup: 8 US fluid ounces, or 236.6 mL.
- US legal cup, used on nutrition labels: 240 mL.
- Metric cup, used in recipes in Australia, New Zealand and some other countries: 250 mL.
Spoons vary too. A US tablespoon is 14.79 mL and a US teaspoon is 4.93 mL. The metric tablespoon is 15 mL and the metric teaspoon is 5 mL. In the US, 3 teaspoons make a tablespoon and 16 tablespoons make a cup (16 × 14.79 = 236.6 mL).
For most cooking, the gap between 14.8 and 15 mL is invisible. The Australian tablespoon is another matter: at 20 mL it is a third larger than the 15 mL kind (20 ÷ 15 = 1.33), which matters for baking powder, salt and strong spices.
Working out which unit is meant
- Look at where the source comes from. US sites use US units, while many British and older Commonwealth sources use imperial ones, although modern recipes often give milliliters.
- Look for a qualifier such as 'US', 'imp' or 'UK' next to the unit, and treat an unmarked pint or gallon with caution.
- Remember that the US also has dry measures. A US dry pint is about 551 mL, used for items like berries, and is not the same as the liquid pint.
- When a recipe offers milliliters or grams, use those and skip the cup conversion altogether.
The volume converter lists US and imperial variants of the gallon, quart, pint, cup and spoon separately, which makes the difference easy to see. For kitchen quantities, the cups to milliliters converter and the teaspoons to milliliters converter cover the most common steps. Volume is only half the story in a kitchen; the article on why a cup of flour weighs less than a cup of sugar explains the other half.
- Volume Converter: Pick a number and two units to convert between 25 metric, US and imperial volume units, from cubic kilometers down to teaspoons. The answer updates as you type.
- Cups to Milliliters Converter: Enter a number of cups and read it as milliliters or liters. Cups and milliliters both measure volume, so the ingredient you select does not change the answer.
- Teaspoons to Milliliters Converter: Enter a number of teaspoons and read the volume in milliliters or liters. The converter uses the US teaspoon (4.93 ml) or the imperial teaspoon (5.92 ml) and rounds milliliters to whole numbers.
This article is general information, not professional advice. See our Disclaimer and Editorial Policy.
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