US, UK and metric cups: which measure does your recipe need?

Before converting a cup-based recipe, check how much the author’s cup holds. One US customary cup of milk is about 237 ml; one metric cup is 250 ml. If you use a 250 ml measure for the US quantity, you add about 13 ml more milk per cup.

The recipe’s measuring guide is the best starting point. Country is a clue, but a British website can publish an American recipe, and an older cookbook may use measures that differ from your current set.

Cup sizes worth recognising

Cup	Volume	What to check
US customary	About 237 ml	The conventional US cooking measure
US nutrition-label cup	240 ml	A labelling definition, not a universal recipe rule
Metric	250 ml	Used in Australian measuring sets and other metric recipes
Imperial, half an imperial pint	About 284 ml	May appear in older recipes; confirm the book’s definition

The 240 ml US labelling definition is set out in 21 CFR §101.9. If a recipe explicitly says its cup is 240 ml, use that value. Do not replace it with 237 ml just because the author is American.

“UK cup” is not a safe instruction by itself. Check for a metric equivalent or a conversion page in the book. A household teacup is not a reliable substitute for a stated measuring cup.

Convert the liquid once, then measure in millilitres

For a recipe specifying US customary cups:

Amount	Approximate volume
½ cup	118 ml
1 cup	237 ml
1½ cups	355 ml
2 cups	473 ml

The kitchen converter offers separate US and metric cups, alongside millilitres, decilitres and regional spoon and fluid-ounce measures. It does not have an imperial-cup option; when a book defines one as half an imperial pint, convert 0.5 UK pints instead.

Use the result as a kitchen measurement, with sensible rounding. The conversion’s extra decimal places do not make the markings on a jug more precise.

Does a larger cup change the recipe?

A metric cup is about 6% larger than a US customary cup. If every ingredient were measured with that same larger cup, in the same way, their relative amounts would stay the same and the batch would be larger. The differences do not compound simply because there are several ingredients.

But recipes also use fixed weights, teaspoons and whole eggs. If you increase the cup-measured flour and milk while leaving the eggs and butter unchanged, you have changed the proportions. Extra batter can also need more room in the tin.

For a soup that you adjust while cooking, the extra liquid may be easy to accommodate. For a cake, follow the stated measures rather than assuming the difference cannot matter—or that it guarantees failure.

The right cup still does not give one universal weight

Flour can settle and pack into a cup; honey fills it quite differently. A volume conversion tells you how much space to fill, not what the ingredient should weigh.

Use the recipe’s weights when it supplies them. Otherwise, consult a matching ingredient chart and keep its preparation notes. The guide to why cups-to-grams depends on the ingredient explains how to use those estimates without treating them as exact.

Keep the rice-cooker cup with the rice cooker

A rice-cooker measure can be smaller than either a US or a metric kitchen cup. Zojirushi’s FAQ describes its supplied cup as about three quarters of a US cup. Use the supplied measure and the matching water marks, following the model’s instructions.

Replacing that cup with a 250 ml kitchen measure while still using the cooker’s marked water line changes the amount of rice relative to water. Label the smaller cup if it is likely to get mixed into your baking set.

Last reviewed 2 October 2026.