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US vs UK vs Metric Cup Sizes

A cup is not a cup: the US cup is 236.588 ml, the metric cup 250 ml and the UK imperial cup 284.131 ml. That 20% spread is the reason converted recipes fail — and the reason to know which country's cup you are holding.

By the UrbiTools editorial team · Rates checked against GOV.UK · Updated

Why three cups exist

The cup was never standardised internationally; each country built its cup from its own pint. The US cup is half a US pint (8 US fluid ounces of 29.5735 ml), giving 236.588 ml. The imperial cup is half an imperial pint (10 imperial fluid ounces of 28.4131 ml), giving 284.131 ml — bigger because the imperial gallon itself is bigger. When Australia and New Zealand metricated, they cut the knot and defined a metric cup of exactly 250 ml. Three pints, three cups, one shared name.

Cup systemMillilitresFluid ouncesUsed in
US customary236.5888 US fl ozUnited States
US legal (labels)2408.12 US fl ozUS nutrition labels
Metric2508.45 US fl ozAustralia, NZ, Canada
Imperial284.13110 imp fl ozOlder UK recipes
Japanese (rice)2006.76 US fl ozJapan

Converting between the cups

The ratios are what you need at the counter: 1 imperial cup = 1.20 US cups; 1 metric cup = 1.057 US cups; 1 imperial cup = 1.137 metric cups. So a British recipe calling for 2 imperial cups of stock needs about 2.4 US cups, and an Australian recipe's 3 metric cups is about 3.17 US cups. For liquids, the cleanest fix is to convert everything to milliliters first — the cups to ml converter does that step — and measure from a jug.

How to spot which cup a recipe means

Check the recipe's other units. If it also uses Fahrenheit, ounces and pounds, it is a US cup. If it uses grams alongside cups, or mentions Australian brands, it is a metric cup. If it says “pint” and means 568 ml, it is imperial. And if the recipe gives weights in grams for the flour and sugar, the cup question disappears for the ingredients that matter most — use the scale for those and cups only for liquids.

The practical rule

For soups, sauces and stews, any cup will do — the 20% spread is inside the tolerance of a simmered dish. For baking, do not trust cups across borders at all: weigh flour, sugar and butter in grams, and convert liquids to milliliters. A recipe that survives that treatment works in any kitchen, whatever cup its author owned.

Browse all our tools from the homepage, or see the full list of guides for more step-by-step explainers.

Sources & official guidance

Frequently asked questions

What is the difference between a US cup and a UK cup?
A US cup is 236.588 ml (8 US fluid ounces) and a UK imperial cup is 284.131 ml (10 imperial fluid ounces) — the UK cup is about 20% bigger.
What is a metric cup?
A 250 ml cup, used in Australia, New Zealand and Canada. It is the easiest to work with because it divides neatly into milliliters.
Which cup do most recipes use?
American recipes use the US cup (236.588 ml). Australian and New Zealand recipes use the metric cup (250 ml). Modern British recipes usually give grams or ml instead of cups at all.
Does the difference matter for baking?
Yes — a 20% difference in flour or liquid changes a cake's texture. For baking, weigh ingredients in grams; the cup is fine for soups, stews and anything forgiving.
What about the Japanese cup?
Japan uses a 200 ml cup for rice cooking — smaller than all three Western cups, and another reason to check a recipe's origin before converting.

Related calculators & guides

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