US Cup vs Metric Cup: 236.6 ml, 240 ml or 250 ml

Three cups, three sizes

The US cup is a customary unit. NIST, the US standards agency, lists it at 236.5882 ml in its conversion tables, and K-State Research and Extension gives the kitchen equivalents that go with it: 1 cup is 8 fluid ounces, 16 tablespoons or 48 teaspoons. The other two cups are rounded metric figures, one set by US labeling rules and one by Canadian law and Australian practice.

Cup	Milliliters	vs US cup	In US tbsp	Where you meet it
US customary cup	236.59 ml	–	16.0	US recipes and measuring cups
US nutrition-label cup	240.00 ml	+1.4%	16.2	Serving sizes on US food labels
Metric cup	250.00 ml	+5.7%	16.9	Canadian labels, Australian recipes

The label cup is 3.4 ml bigger than a US measuring cup, less than a teaspoon. The metric cup is 13.4 ml bigger, close to a full US tablespoon per cup. You can convert any of these with the cooking measurement converter, which keeps the US, label and metric units apart.

The US customary cup: 236.6 ml

This is the cup in American measuring sets and in nearly every US recipe. It comes from the US gallon: a cup is 1/16 of a gallon, 8 US fluid ounces. In milliliters that works out to 236.5882 ml, which NIST rounds to 236.5882 ml and which is often rounded to 237 ml. A US tablespoon is 1/16 of the cup, 14.79 ml, and a teaspoon 1/3 of a tablespoon, 4.93 ml.

A cup of water weighs 237 g in USDA FoodData Central, so for water and watery liquids the milliliter and gram figures nearly match. For anything else the weight depends on the ingredient, which is the job of the cups to grams converter.

The nutrition-label cup: 240 ml

US food labels use their own cup. The FDA rule for nutrition labeling, 21 CFR 101.9(b)(5)(viii), says that for labeling purposes a cup means 240 ml, a tablespoon 15 ml and a teaspoon 5 ml. When a label reads "1 cup (240 mL)", that is the reason. It is a rounding convention for labels and does not change the size of measuring cups. The guide on fluid ounces vs ounces covers the label units in more detail; for cooking, the 1.4 percent difference does not matter.

The metric cup: 250 ml

A metric cup is a round quarter liter. Two official sources confirm where it is used:

Canada. The Safe Food for Canadians Regulations, section 241(3), say that when a package states servings in cups or tablespoons, one cup is equivalent to 250 ml and one tablespoon to 15 ml.
Australia. Healthdirect, the government-funded health information service, states that in Australia 1 cup is about 250 ml.

A metric cup holds 16.9 US tablespoons, or 16.7 metric tablespoons of 15 ml. NIST notes that metric cup and spoon measures are slightly larger than US customary ones and can often be used interchangeably. In baking, where flour, liquid and leavening are balanced against each other, the gap is worth a second look.

The same amount in each cup

Each row is one recipe amount, measured three ways. The last column is how much more a metric cup measure holds than a US one, in US teaspoons.

Recipe says	US cup	Label cup	Metric cup	Metric extra
1/4 cup	59 ml	60 ml	63 ml	0.7 tsp
1/3 cup	79 ml	80 ml	83 ml	0.9 tsp
1/2 cup	118 ml	120 ml	125 ml	1.4 tsp
1 cup	237 ml	240 ml	250 ml	2.7 tsp
2 cups	473 ml	480 ml	500 ml	5.4 tsp
3 cups	710 ml	720 ml	750 ml	8.2 tsp
4 cups	946 ml	960 ml	1,000 ml	10.9 tsp

For a quarter cup of oil the difference is under a teaspoon. At 4 cups it is 54 ml, which is about 1/4 of a US cup. A recipe that uses several cups of liquid and flour in a fixed ratio is where it shows up.

Spoons follow the same pattern

Spoon	US customary	US label	Canada
Tablespoon	14.79 ml	15 ml	15 ml
Teaspoon	4.93 ml	5 ml	not set in s. 241

The tablespoon gap is small: a 15 ml spoon holds 0.21 ml more than a US tablespoon, about 1.4 percent. For baking soda, salt or yeast that difference is lost in how level the spoon is. If a recipe states the spoon size in milliliters, go by that number rather than the name of the spoon.

What about British recipes?

The UK has no legal cup. Schedule 1 of the Weights and Measures Act 1985 lists the imperial pint at 568.26 ml, the gill and the fluid ounce, but no cup or tablespoon. If a British recipe says "half a pint", that is 284 ml, well above a US cup. If it says "cup" with no other figure, there is no standard to convert from, and a weight elsewhere in the recipe is the better guide.

Worked examples

A Canadian recipe asks for 2 cups of milk

Written for metric cups, that is 500 ml. Two US cups hold 473 ml, so you come up 27 ml short, about 1.8 US tablespoons. If the recipe also prints 500 ml, measure 500 ml in a jug with metric markings.

An American recipe used with a metric cup set

Three US cups of stock are 710 ml. In metric cups that is 2.84, a little under 2 3/4 metric cups. Filling three metric cups adds 40 ml, which a soup absorbs without trouble.

Scaling a recipe up

Doubling or tripling a recipe also doubles or triples the gap between cup systems. Scale the recipe first with the recipe scaler, then convert the totals to milliliters with the volume converter and measure in one system throughout.

Which cup to use

Use the cups from the recipe's own country. A US recipe means 236.6 ml, a Canadian or Australian one 250 ml.
Do not mix sets in one recipe. If the flour goes in with a metric cup and the milk with a US cup, the ratio shifts by about 5 percent.
When a recipe gives grams or milliliters next to the cups, use those. NIST calls weighing ingredients on a kitchen scale best practice for accuracy.
Ignore the 240 ml label cup in the kitchen. It only matters when you compare a nutrition label with an amount you measured.

For butter in sticks and grams, see the guide to butter measurements.

Frequently asked questions

How many milliliters are in a US cup?

236.59 ml. NIST lists the US cup at 236.5882 ml, which is 8 US fluid ounces. Recipes and converters often round it to 237 ml, and US nutrition labels use 240 ml.

Is a metric cup the same as a US cup?

No. A metric cup is 250 ml, about 5.7 percent more than a US cup, or roughly 0.9 US tablespoons extra per cup. NIST says metric cup and spoon measures can often be used interchangeably with US ones in everyday cooking, but the gap adds up in recipes with several cups.

Why does a US food label say 1 cup is 240 ml?

FDA rules define the cup as 240 ml for nutrition labeling only, along with a 15 ml tablespoon and a 5 ml teaspoon. It is a rounded labeling unit, not the cup in your drawer.

What size cup does Canada use?

For serving statements on food packages, the Safe Food for Canadians Regulations say one cup is equivalent to 250 ml and one tablespoon to 15 ml. When a recipe prints milliliters next to the cups, follow the milliliters.

Is there an imperial or British cup?

Not as a legal unit. The UK Weights and Measures Act lists the pint, gill and fluid ounce, but no cup or tablespoon. So a British recipe that says "cup" has no legal size behind it; look for a weight or a milliliter figure in the same recipe. Half an imperial pint is 284 ml, if a recipe says "half a pint".

Sources

Written by Tobias. Updated November 2, 2026.