Cups to mL: US, Metric, and UK Cups
A US cup is 236.6 ml. But "cup" is not one fixed size: the US legal cup is 240 ml, the metric cup used across Australia and New Zealand is 250 ml, and the UK imperial cup is 284 ml. Pick the wrong one and a recipe drifts off by up to 20 percent. The converter lets you switch standards; this page shows all four.
The four cup standards: US 236.6 ml · US legal 240 ml · Metric 250 ml · UK imperial 284.1 ml.
Which cup is which
The US customary cup (236.6 ml) is what almost every American recipe means, and it is the default here. The US legal cup (240 ml) is defined for nutrition labels and is close enough that most cooks never notice the 3.4 ml gap. The metric cup (250 ml) is the round-number standard in Australia and New Zealand. The UK imperial cup (284.1 ml), exactly half an imperial pint, appears only in older British books, since modern UK recipes weigh ingredients in grams.
Cups to mL chart
The two columns below cover the two you are most likely to meet: the US customary cup and the 250 ml metric cup.
| Cups | US cup (236.6 ml) | Metric cup (250 ml) |
|---|---|---|
| 1/4 cup | 59.1 ml | 62.5 ml |
| 1/3 cup | 78.9 ml | 83.3 ml |
| 1/2 cup | 118.3 ml | 125 ml |
| 2/3 cup | 157.7 ml | 166.7 ml |
| 3/4 cup | 177.4 ml | 187.5 ml |
| 1 cup | 236.6 ml | 250 ml |
| 2 cups | 473.2 ml | 500 ml |
Does the difference actually matter?
Between the US cup and the metric cup the gap is about 13 ml per cup, roughly 5 percent. For a splash of milk or a cup of broth that is invisible. Where it bites is in recipes that stack several cups of flour or sugar, or in delicate work like macarons and bread where hydration is tuned tightly. Two cups of flour measured in metric cups instead of US cups is nearly 27 ml of extra volume, enough to shift a dough. The UK imperial cup is the real outlier at 284 ml, almost a fifth larger than a US cup, so an old British recipe read with a US cup will come out noticeably dry. When a recipe's success depends on ratios, weigh in grams and the cup standard stops mattering at all.
Which standard is my recipe using?
Go by where the recipe comes from. American sites and cookbooks mean the 236.6 ml US cup. Recipes from Australia, New Zealand, and most modern European sources that use cups mean the 250 ml metric cup. An older British book, especially anything pre-1970s, may mean the 284 ml imperial cup. When in doubt, a US cup is the safest default, and for anything where precision matters, weigh the ingredient in grams instead of measuring by volume. The ounces in a cup and tablespoons in a cup pages break the cup down further.