How Many Ounces in a Cup?
A US cup holds 8 fluid ounces by volume. That figure never changes for liquids: 1 cup of water, milk, or oil is always 8 fl oz. The catch is that fluid ounces measure volume, not weight, so a "cup" of a dry ingredient rarely weighs 8 ounces on a scale. The converter handles both.
Quick answer: 1 US cup = 8 fluid ounces = 236.6 ml. Half a cup is 4 fl oz, a quarter cup is 2 fl oz.
Fluid ounces vs weight ounces
This is the confusion that ruins recipes. A fluid ounce measures how much space something takes up. A weight ounce, measured on a scale, tells you how heavy it is. They only match for water, where 1 fluid ounce of water happens to weigh almost exactly 1 ounce.
For everything else they diverge. Fill a 1-cup measure with all-purpose flour and you have 8 fluid ounces of flour by volume, but on a scale it weighs only about 4.2 ounces (120 grams). Flour is light and airy, so the same volume weighs roughly half what an equal volume of water would. A cup of honey, which is dense, weighs closer to 12 ounces. When a recipe says "4 oz of flour" it almost always means weight, so reach for a scale, not a measuring cup. For weight conversions, see grams to ounces.
Cups to fluid ounces chart
| Cups | Fluid ounces | Milliliters |
|---|---|---|
| 1/4 cup | 2 fl oz | 59.1 ml |
| 1/3 cup | 2.67 fl oz | 78.9 ml |
| 1/2 cup | 4 fl oz | 118.3 ml |
| 2/3 cup | 5.33 fl oz | 157.7 ml |
| 3/4 cup | 6 fl oz | 177.4 ml |
| 1 cup | 8 fl oz | 236.6 ml |
| 2 cups | 16 fl oz | 473.2 ml |
| 3 cups | 24 fl oz | 709.8 ml |
| 4 cups | 32 fl oz | 946.4 ml |
One US fluid ounce equals 29.57 ml, so every cup above is simply the number of fluid ounces times 29.57. Two cups make a US pint (16 fl oz) and four cups make a quart (32 fl oz).
A note on UK cups
British recipes rarely use cups, but when they do the UK imperial cup is larger: 284 ml, which works out to about 9.6 US fluid ounces rather than 8. If you are following an older British book that measures in cups, expect every cup to be roughly 20 percent bigger than a US cup. Modern UK recipes usually give grams instead. The cups to mL guide lays out all four cup standards side by side.