A "cup" is not one size
The mL value is fixed; the cup you divide by is not. American recipes use the 236.6 mL customary cup, most of the rest of the metric world uses a round 250 mL, and older British recipes use a 284 mL imperial cup. Pick the wrong one and a full cup is off by up to 20%.
The three cups people actually meet
A UK cup holds about 20% more than a US cup. The everyday clash is the smaller one: a metric cup is 250 mL against the US 236.6 mL, roughly a 6% difference that stacks up across a multi-cup recipe.
Quick reference
| mL | US cups | Metric cups | Practical |
|---|---|---|---|
| 120 | 0.51 | 0.48 | ½ cup |
| 237 | 1.00 | 0.95 | 1 cup (US) |
| 240 | 1.01 | 0.96 | 1 cup (FDA label) |
| 250 | 1.06 | 1.00 | 1 cup (metric) |
| 500 | 2.11 | 2.00 | 2 cups (metric) |
| 1000 | 4.23 | 4.00 | 1 litre |
- Label cup vs recipe cup — US nutrition labels round to a 240 mL "legal" cup, while US recipes use 236.6 mL. Close enough for cooking, worth the difference in baking.
- Volume, not weight — a cup measures space, so 1 cup of flour (about 125 g) and 1 cup of sugar (about 200 g) weigh very differently. For accuracy, convert to grams.
Common questions
How many milliliters are in a cup?
It depends which cup. A US customary cup is 236.6 mL, the US legal cup used on nutrition labels is 240 mL, a metric cup (Australia, New Zealand, Canada) is 250 mL, and a UK imperial cup is 284 mL.
How many cups is 500 mL?
500 mL is 2.11 US cups, or exactly 2.00 metric cups. The metric conversion is cleaner because 250 mL times 2 lands right on 500.
Which cup should I use for a recipe?
Match the recipe origin: US recipes mean the 236.6 mL cup, Australian and NZ recipes mean the 250 mL metric cup. The gap is about 6%, which shows up in baking, so weighing in grams is the reliable fix.
