Cup Sizes Around the World: US, Metric, Imperial & Japanese
A cup is 236.6 ml in America, 250 ml in Australia and 284 ml in older British books. Here is which one your recipe means and what to do about it.
A cup is 236.6 ml in America, 250 ml in Australia and 284 ml in older British books. Here is which one your recipe means and what to do about it.
The word "cup" in a recipe is one of the least standardised units in cooking. Five different cups are in active use, and the largest is 42% bigger than the smallest.
The five cups
The US customary cup is the one nearly every recipe on the internet means, because so much recipe content is American. It is defined as half a US pint: 236.5882365 ml exactly.
Which cup does your recipe mean?
Go by origin, not by the word.
American blogs, American cookbooks, most global recipe sites — US customary, 236.6 ml.
Australian and New Zealand recipes — metric cup, 250 ml. Australia standardised this deliberately so a litre would be exactly four cups.
How much the difference matters
Six percent between a US and a metric cup sounds trivial. Scale it up and it stops being trivial.
Twenty-one grams of flour in a cake is roughly an eighth of a cup — enough to firm up a crumb that was meant to be tender. Forty millilitres of water in a bread dough is a visible change in hydration.
The imperial cup is worse. At 284 ml it is 20% larger, so three imperial cups of flour is 450 g against 375 g for US cups. That is not a nudge, it is a different recipe.
Tablespoons diverge too
The cup is not the only unit that shifts.
Australia's 20 ml tablespoon is the outlier, and it matters most for the ingredients measured in single spoonfuls. An Australian recipe calling for a tablespoon of baking powder wants a third more than an American one — enough to taste.
If you are cooking Australian recipes with US spoons, use one tablespoon plus one teaspoon wherever it says one tablespoon.
Pints and gallons, where it gets worse
The imperial system did not simply scale the American one — it went a different way.
Note the reversal: the imperial fluid ounce is smaller, but there are more of them in a pint, so the imperial pint is larger by about 20%. A British recipe calling for a pint of cream wants nearly a fifth more than a US pint delivers.
The fix that ends the problem
Use grams.
Weight is the same everywhere. A gram is a gram in Sydney, Chicago and Osaka, and no amount of national tradition changes it. This is exactly why professional recipes and every serious modern cookbook are written in weight.
If a recipe gives both cups and grams, use the grams and ignore the cups entirely — the ambiguity vanishes.
A quick reference for converting between cup systems
US cup → metric cup: multiply by 0.946
Metric cup → US cup: multiply by 1.057
US cup → imperial cup: multiply by 0.833
Frequently asked questions
How big is an Australian cup?
250 ml — the metric cup, also used in New Zealand and Canada. It is about 5.7% larger than a US cup.
Is a UK cup the same as a US cup?
Modern British recipes almost always use grams and millilitres rather than cups. Where an older British book does say cup, it usually means the imperial cup of 284 ml, which is 20% larger than a US cup.
Does the cup difference actually matter?
For soups, stews and anything forgiving, no. For cakes, bread and pastry, yes — a 6% change in flour or liquid is enough to alter the texture, and 20% will change the recipe entirely.
What is a US legal cup?
240 ml, used for nutrition labelling in the United States. It is a rounded version of the 236.6 ml customary cup and only appears on packaging, not in recipes.
How do I know which cup a recipe means?
Go by where it was written. American sites and books mean 236.6 ml; Australian and New Zealand ones mean 250 ml. If the recipe gives grams as well, use the grams and the question disappears.