A US customary cup is 236.588 mL, usually rounded to 237 mL. US nutrition labels use a rounder, legal value of exactly 240 mL per cup. To convert, multiply cups by 236.588 (or by 240 for label math): 2 cups is 473.2 mL, or 480 mL on a label.
How many mL are in a cup?
NIST lists the US cup as 236.5882 mL. This follows from the US cup being 8 fluid ounces of 29.57353 mL each: 8 × 29.57353 = 236.588 mL. The milliliter is one thousandth of a liter, so a cup is a little under a quarter of a liter.
Why do some sources say 240 mL?
US food regulation defines a cup differently for one purpose. Under 21 CFR 101.9(b)(5)(viii), a cup on a nutrition label means 240 mL, a tablespoon 15 mL, a teaspoon 5 mL and a fluid ounce 30 mL. The US legal cup is a rounding for labels, not a second physical cup. 240 ÷ 236.588 = 1.0144, so the label cup is about 1.4% larger.
Cups to mL chart
| Cups | US customary (mL) | Nutrition label (mL) |
|---|---|---|
| 1/4 cup | 59.1 | 60 |
| 1/3 cup | 78.9 | 80 |
| 1/2 cup | 118.3 | 120 |
| 3/4 cup | 177.4 | 180 |
| 1 cup | 236.6 | 240 |
| 1 1/2 cups | 354.9 | 360 |
| 2 cups | 473.2 | 480 |
| 3 cups | 709.8 | 720 |
| 4 cups | 946.4 | 960 |
Other values are on the cups to ml converter.
Which value should be used?
- Cooking and baking: 237 mL (or 236.6 mL). A 1.4% difference changes a cup of liquid by about 3.4 mL, under a teaspoon.
- Reading a nutrition label: 240 mL, because serving sizes in "cups" were set with that value.
- Exact conversions: 236.588 mL, from NIST.
Worked examples
Example 1: a 500 mL ingredient
500 ÷ 236.588 = 2.11 cups. On the label basis, 500 ÷ 240 = 2.08 cups.
Example 2: a recipe for 3/4 cup of milk
3/4 × 236.588 = 177.4 mL, close to the label value of 180 mL.
Example 3: a 1 liter bottle
1,000 ÷ 236.588 = 4.23 cups. A recipe listing 4 cups needs about 946 mL, a little under the bottle.
Does the cup differ in other countries?
Yes. Measuring cups are not the same everywhere, which is why a recipe from another country can come out different. NIST notes that customary units such as cups can differ in meaning from country to country. Metric vs imperial covers the near-twin units, and how many ounces in a cup separates fluid from weight ounces. For dry ingredients, volume is not weight: see cups to grams.