US, Metric and UK Cups: How Big Is a Cup?
A US cup is 236.6 ml, a metric cup is 250 ml, and older British recipes may use a larger cup. Here is how cup and spoon sizes differ, and when it matters.
"One cup" sounds like a fixed amount, but it is not the same everywhere. If you use recipes from different countries, the cup and even the tablespoon can be different sizes.
The main cup sizes
| Cup | Volume | Where you will see it |
|---|---|---|
| US customary cup | 236.6 ml | Most American recipes and measuring cups |
| US "legal" cup | 240 ml | US nutrition labels |
| Metric cup | 250 ml | Australia, New Zealand, Canada and many other countries |
| Imperial cup | about 284 ml | Older British recipes (half an imperial pint) |
| Japanese cup | 200 ml | Japanese recipes |
All the weights on this site use the US customary cup of 236.6 ml, because that is the cup American recipes and measuring sets use.
Does the difference matter?
Between the US cup and the metric cup, the difference is about 6%. For a single cup of milk in a pancake batter, that rarely matters. For flour in a cake, or across several cups of ingredients, it adds up. The imperial cup is about 20% larger than a US cup, which is enough to change a recipe noticeably.
The simplest way to avoid the problem is to weigh dry ingredients. A recipe that says 250 g of flour means the same thing in every country.
Spoons differ too
- US tablespoon: about 14.8 ml. There are 16 tablespoons in a US cup.
- Metric tablespoon (UK, Canada, New Zealand): 15 ml. Practically the same as the US tablespoon.
- Australian tablespoon: 20 ml, equal to four teaspoons rather than three. This is the one that catches people out: an Australian recipe's tablespoon holds a third more than an American one.
- Teaspoon: about 5 ml almost everywhere.
Volume vs weight
A milliliter measures space, a gram measures weight. They only line up for water: 1 ml of water weighs 1 g, so a US cup of water weighs about 237 g. Other ingredients are heavier or lighter than water. A cup of honey weighs about 340 g, while a cup of flour weighs about 120 g. That is why you cannot convert cups to grams without knowing the ingredient, and why each ingredient on this site has its own chart.
Fluid ounces vs ounces
A US cup is 8 fluid ounces, which is a volume. An ounce on a scale is a weight (28.35 g). They are only equal for water and liquids of similar density. "8 oz of flour" by weight is nearly two cups, not one.
Practical tips
- Check where a recipe comes from before measuring. Australian and New Zealand recipes use metric cups and 20 ml tablespoons.
- If a recipe gives both cups and grams, use the grams.
- Measuring sets sold in the US are US customary. Sets sold elsewhere are usually metric, and many are labeled with milliliters.