Cup Sizes Explained
A US customary cup is 236.59 mL, a US legal cup is 240 mL, a metric cup is 250 mL and a historic imperial cup is 284 mL.
By Piero Nanni · Last checked
The four cups
The spread from smallest to largest is 20 percent. Across a recipe using four cups of liquid that is nearly 200 mL, enough to change a batter into a pour or a dough into a paste.
| Cup | Volume | Defined as | Used in |
|---|---|---|---|
| US customary | 236.59 mL | 8 US fluid ounces, 1/16 US gallon | American recipes and measuring cups |
| US legal | 240 mL | Fixed by the FDA for labelling | US nutrition labels, many modern cookbooks |
| Metric | 250 mL | A quarter of a litre | Australia, New Zealand, modern Canadian recipes |
| Imperial | 284.13 mL | 10 imperial fluid ounces, half an imperial pint | Older British recipes |
How to tell which one a recipe means
Origin is the best clue. American sources mean the customary cup, though many round it to 240 mL and the difference of 3.4 mL per cup is small enough to ignore in most cooking. Australian and New Zealand sources mean 250 mL. British recipes written since the 1970s tend to use weights in grams rather than cups at all.
A useful cross-check is the tablespoon. If a recipe treats a cup as 16 tablespoons it is American. If it treats a cup as 16 tablespoons of 20 mL each, it is Australian, where the tablespoon is four teaspoons rather than three.
Why weighing beats measuring for dry ingredients
For solids the cup is unreliable regardless of which cup you own, because it measures volume and bakers care about mass. A cup of flour weighs anywhere from about 120 g to 150 g depending on whether it was scooped, spooned or sifted, a variation of up to 25 percent within a single kitchen.
This is why professional and European recipes give flour, sugar and butter in grams. If a recipe offers both, use the weights: they remove both the which-cup question and the how-packed question at once.
Frequently Asked Questions
How many mL is a cup?
It depends: 236.59 mL in the US, 240 mL on US labels, 250 mL in Australia and New Zealand, 284 mL in older British recipes.
Is a US cup the same as a metric cup?
No. A US customary cup is 236.59 mL against the 250 mL metric cup, about 5.6 percent smaller.
How much does a cup of flour weigh?
Roughly 120 to 150 g depending on how it was filled, which is why weighing is more reliable than measuring.
How many tablespoons are in a cup?
Sixteen US tablespoons make a US cup. An Australian cup is 16 Australian tablespoons of 20 mL, which is a different volume.