How many ounces are in a cup?
Quick answer
A US cup holds 8 fluid ounces (about 237 ml). By weight it depends on what’s inside: a cup of water weighs about 8.3 oz, but a cup of all-purpose flour weighs only about 4.25 oz.
That gap is the most common reason a baking recipe goes wrong. Volume ounces work fine for liquids, but for dry ingredients, weight is far more reliable.
Converter
How much does a cup weigh?
Approximate weights for one level US cup:
| Ingredient | Ounces | Grams |
|---|---|---|
| Water or milk | 8.3 oz | 237 g |
| Butter | 8 oz | 227 g |
| Granulated sugar | 7 oz | 200 g |
| Brown sugar (packed) | 7.5 oz | 213 g |
| All-purpose flour | 4.25 oz | 120 g |
| Rolled oats | 3 oz | 85 g |
Flour varies the most. Scooping straight from the bag packs it down and can add 20% or more, which is why many bakers spoon flour into the cup and level it off, or simply use a scale.
Are all cups the same size?
Not quite. The US customary cup is about 237 ml, but nutrition labels use a rounded “legal cup” of 240 ml. Australia, Canada and New Zealand often use a metric cup of 250 ml. The old UK imperial cup was bigger still, at about 284 ml, though modern British recipes mostly use grams and milliliters.
For bigger amounts, there are 16 cups in a gallon, which works out to 128 ounces in a gallon.
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