Two Cup Sizes
A US customary cup is 236.588 mL (8 US fluid ounces). A metric cup, used in Australia, New Zealand, and some other countries, is 250 mL. The difference is about 5.6%, enough to matter in baking. A US recipe's '1 cup' and an Australian recipe's '1 cup' are not the same volume.
Avoiding the Trap
When following a recipe from another country, check which cup it uses, or — better — convert everything to milliliters or grams. Recipes that list grams are immune to the cup-size problem entirely.
Reference
| Cup type | Milliliters | Fluid ounces |
|---|---|---|
| US cup | 236.6 | 8 |
| Metric cup | 250 | 8.45 |