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US cup vs metric cup vs UK cup: what’s the difference?

Updated September 29, 2026

“1 cup” sounds like a fixed amount, but there are several cups in use around the world. The difference is small for most recipes, but it can matter in baking.

The main cup sizes

  • US customary cup: 236.6 ml. Used by almost all American recipes and measuring cups sold in the US.
  • US legal cup: 240 ml. Used on US nutrition labels. You will rarely see it in recipes.
  • Metric cup: 250 ml. Used in Australia, New Zealand and Canada.
  • UK imperial cup: 284 ml. Found in older British recipes. Modern UK recipes use grams.

Does it matter?

A metric cup holds about 6% more than a US cup. For soups, stews and most savory cooking, that makes no real difference. In baking, 6% more flour or sugar can change the texture, so it is worth using the cup the recipe was written for, or converting to grams.

How to tell which cup a recipe uses

Look at where the recipe comes from. American websites and books use the US cup. Australian and New Zealand recipes use 250 ml cups, and often list tablespoons of 20 ml as well. If you are unsure, weights in grams remove the question completely.

Converting with the right cup

Every converter on this site has a cup size option. Choose “Metric cup (250 ml)” for Australian or New Zealand recipes and the grams update automatically. See also our full ml in a cup chart.