Cup Sizes in Cooking

Updated September 2026 · Baking Resources

There are four cup sizes in cooking, and they are not interchangeable. A US customary cup is 236.588 mL, the one in your American kitchen drawer. A metric cup is 250 mL, used in Australia, New Zealand, Canada and most of metric Europe. A US legal cup is 240 mL, which exists only for nutrition labels. And an imperial cup is 284.13 mL, from British cookbooks printed before about 1970.

So the metric cup is 5.7 percent bigger than the American one, and the old imperial cup is a full 20 percent bigger. Whether that ruins your bake depends entirely on one thing, which almost nobody explains, and we'll get to it below.

Need the number now? Our free cups to mL converter switches between all four standards and gives you the answer in kitchen fractions.

Updated September 2026

Cup sizes in cooking: the four standards side by side

The American figure isn't arbitrary, even though it looks it. A US fluid ounce is defined as exactly 29.5735295625 mL, and a cup is 8 of them. Multiply it out and you get 236.5882365 mL, which everyone sensibly rounds to 236.588.

The metric cup is 250 mL because it's a quarter of a liter, and someone decided that was tidier than importing an American number.

The imperial cup is 10 imperial fluid ounces, and an imperial fluid ounce is a different size from an American one. That's the reason the gap is so large, and it's the reason a very old British recipe is genuinely dangerous to make with American cups.

The US legal cup at 240 mL is the odd one out. It's a rounding created by the FDA so that serving sizes on packages come out in whole numbers. No recipe writer uses it, and no measuring cup sold in a store is made to it. If you see 240 mL quoted as "one cup" in a conversion table, that table is quoting a labeling rule rather than a kitchen measure.

How to tell which cup your recipe means

Nobody labels this. You have to read the signals, and there are five reliable ones.

1. Fahrenheit and cups together means American. If the oven is set in °F, the cup is 236.588 mL. This is the strongest single tell.

2. Grams alongside cups means metric. A recipe that says "250 g (2 cups) flour" was written by someone working in grams, so the cup is 250 mL and the gram figure is the one to trust.

3. Celsius, cups, and no grams means metric cup. Australian and New Zealand food sites do this constantly. Check the domain: a .com.au or .co.nz recipe uses 250 mL cups and a 20 mL tablespoon.

4. Vocabulary gives it away. "Caster sugar", "plain flour", "self-raising", "icing sugar", "bicarbonate of soda" and "double cream" all point outside the United States. American recipes say superfine, all-purpose, self-rising, powdered sugar, baking soda and heavy cream.

5. A book older than about 1970 with British spelling may be using the imperial cup. Modern British recipes almost never use cups at all, because British home cooking switched to kitchen scales decades ago. If a current UK recipe does print cups, it's usually a US conversion added for American readers.

When the signals conflict, weigh instead of measuring. Our grams to cups converter will get you from one to the other for any ingredient, and it settles the argument permanently.

What the difference actually costs you, ingredient by ingredient

Here's what one cup of the same ingredient weighs on each standard. These come straight from the density figures behind our own calculators, so the numbers here and the numbers in the tools agree.

Look down the flour row. Seven grams between a US and a metric cup. That's less than a tablespoon, and it's smaller than the error you introduce by scooping the cup into the bag instead of spooning flour in. Our how to measure flour guide covers that gap, which runs from 125 g spooned to 145 g scooped, a 16 percent swing inside one country's own standard.

Now look at the honey row. Sixty-eight grams between US and imperial. That one will show up in the finished food.

The insight nobody mentions: a uniform error mostly cancels out

This is the part that changes how you think about it.

If a recipe measures everything in cups, and you use the wrong cup for everything, you haven't changed the recipe. You've scaled it. Every ingredient is 5.7 percent larger, the ratios are identical, and the cake is a cake. You just made slightly more of it.

The damage happens when the cup error is partial. That's when the ratios break, and ratios are what baking runs on.

Partial errors look like this:

• Cups mixed with spoons. An Australian recipe says 2 cups of flour and 2 teaspoons of baking powder. Use American cups and the flour drops 5.7 percent while the baking powder stays put, so you're now running 6 percent more leavening than intended. Small, survivable, but it's a real change.
• Cups mixed with grams. "2 cups flour, 100 g butter" on a metric recipe. The flour shrinks, the butter doesn't, and the dough comes out richer and softer.
• Cups mixed with can or package sizes. A 14 oz can of condensed milk is a fixed amount. The cups around it aren't.
• Anything with yeast, baking powder or baking soda in a spoon measure. These are the ingredients where a few percent shows up as taste, and where our tablespoons to cups chart is worth a look before you start.

So the rule is short. All cups, no worries. Cups plus anything else, convert first.

Worked example: an Australian cake in an American kitchen

The recipe, from an Australian site, using 250 mL cups: 2 cups self-raising flour, 1 cup caster sugar, 125 g butter, 2 eggs, 1 cup milk, 1 teaspoon vanilla.

Notice the problem straight away. The butter is in grams, everything else is in cups. That's a partial error, so the ratios will shift if you just use your American cups.

Step 1. Convert the cups to volume. 2 metric cups is 500 mL. 1 metric cup is 250 mL.

Step 2. Turn that into US cups. 500 divided by 236.588 is 2.11 US cups of flour. 250 divided by 236.588 is 1.06 US cups of sugar and the same of milk.

Step 3. Or skip straight to weight, which is easier.

Step 4. Sanity check the size of the mistake. If you'd ignored all of this and used flat American cups, you'd have run 250 g of flour against 125 g of butter instead of 264 g against 125 g. That's a fat ratio of 0.50 instead of 0.47, about 6 percent richer. The cake would still be good. It would spread a little more and brown a little faster.

That's the honest verdict on the metric-versus-US cup: it's a real difference and it's worth getting right, but on a plain cake it's a nudge, not a disaster.

Now run the same recipe as if it were imperial. 2 imperial cups of flour is 300 g against 125 g of butter, a fat ratio of 0.42. That's 12 percent leaner than the recipe intended, plus 20 percent more milk. Dry, tough, and noticeably different. Imperial is the standard you cannot ignore.

Self-rising, caster and the vocabulary trap

Getting the cup right doesn't help if you got the ingredient wrong, and cup-standard confusion travels with ingredient-name confusion.

That last row causes more ruined sauces than any cup measurement ever has. If a British or Australian recipe says cornflour, it means cornstarch. If an American recipe says corn flour, it means finely ground cornmeal.

Does the cup change with what's in it?

No, and this is the point people get backwards most often.

A cup is a fixed volume. One cup of flour and one cup of honey are both 236.588 mL. What changes is the weight, because flour is airy and honey is dense. That's why the same US cup is 125 g of flour and 340 g of honey.

The confusion comes from the "8 ounces in a cup" phrase, which is only true for fluid ounces, and only ever measures volume. Eight weight ounces of flour is nearly two cups. Our oz to cups guide untangles that pair properly, because it's the most expensive misunderstanding in the whole conversion business.

You also have two different physical cups in your kitchen, and they measure the same volume in different ways. Nested dry cups are filled to the brim and leveled off with a straight edge. Glass liquid measures are filled to a line below the rim so you can carry them. Using a liquid measure for flour overpacks it by 10 to 15 percent, and using a dry cup for milk means spilling or under-filling. The full method is in our guide to measuring baking ingredients.

The tablespoon problem rides along with the cup

If a recipe uses a foreign cup, it uses foreign spoons too, and one of those is a genuine trap.

The Australian tablespoon holds four teaspoons instead of three, which is 33 percent more, and no recipe warns you. On oil it barely matters. On baking powder it's the difference between a good cake and a bitter, collapsed one.

Teaspoons are the one measure that's effectively universal at 5 mL, or 4.93 mL in strict US terms. If an Australian recipe worries you, convert its tablespoons to teaspoons and work in those.

Where cup sizes in cooking actually matter, and where they don't

Ignore the difference when:

• Everything in the recipe is measured in cups.
• The dish is forgiving: soup, stew, oatmeal, granola, pancake batter, most cookie doughs.
• The gap is between US customary and US legal, which is 1.4 percent, or about half a teaspoon per cup.

Convert properly when:

• The recipe mixes cups with grams, spoons or package sizes.
• The recipe is imperial, or you suspect it is.
• You're baking bread, macarons, choux, laminated pastry, or anything where hydration is the recipe.
• The recipe scales a leavener, salt or spice in a spoon measure.

Always weigh when:

• You want the same result twice.
• You're converting between systems at all. Grams are grams everywhere, which is the whole reason to use them.

Our kitchen converter handles the volume side across all four cup standards, and the full baking conversion chart puts cups, grams, ounces and oven temperatures on one page if you'd rather print something and stick it inside a cupboard door.

Frequently asked questions

How many mL is 1 cup?

236.588 mL for a US customary cup, which is what American recipes mean. 240 mL for the US legal cup used on nutrition labels. 250 mL for a metric cup, standard in Australia, New Zealand, Canada and metric Europe. 284.13 mL for an old imperial British cup. If nothing tells you which, and the oven temperature is in Fahrenheit, it's 236.588.

Is an Australian cup the same as a US cup?

No. An Australian cup is 250 mL against a US cup of 236.588 mL, so it's about 6 percent larger. The Australian tablespoon is the bigger problem: it's 20 mL, or four teaspoons, where every other country uses 15 mL and three teaspoons. On leavening amounts that 33 percent overshoot genuinely spoils a bake.

What is the US legal cup, and does it matter in cooking?

It's 240 mL, defined by the FDA so that nutrition labels come out in round numbers. It matters for reading a package and never for cooking. No recipe is written to it and no measuring cup is manufactured to it. The 3.4 mL gap between 240 and 236.588 is about two thirds of a teaspoon, which is inside the error of any hand-leveled cup anyway.

Do British recipes use cups?

Modern ones mostly don't. British home cooking runs on kitchen scales, so a current UK recipe gives you grams and milliliters. When a British site does print cups, it has usually added an American conversion for its overseas readers, so read it as 236.588 mL. Only genuinely old British cookbooks, printed before about 1970, use the 284.13 mL imperial cup.

What is a Japanese cup in cooking?

200 mL, which is 15 percent smaller than a US cup and 20 percent smaller than a metric one. Japanese rice cookers use a different measure again, a 180 mL cup called a go, which is why the cup that comes with the cooker doesn't match your measuring cups. Use the cup that came in the box for rice and a real measure for everything else.

Does using the wrong cup size ruin a recipe?

Usually not, if the whole recipe is in cups, because you've scaled every ingredient by the same amount and the ratios still hold. It does cause trouble when cups sit alongside grams, spoons or fixed package sizes, because then only some ingredients shift. Imperial is the exception at 20 percent off, which breaks a recipe outright.

Should I just weigh everything instead?

Yes, if you want the same result every time. A gram is a gram in every country, so weighing removes the cup question, the scoop-versus-spoon question and the packed-versus-loose question all at once. Set a bowl on the scale, hit tare, and add ingredients one after another into the same bowl. It's fewer dishes than cups, which surprises people the first week.

Why do conversion charts disagree with each other?

Because they're quoting different standards without saying so. A chart that prints 240 mL is quoting the US legal cup. One that prints 250 mL is metric. One that prints 236.588 is US customary. None of them is wrong, they're just answering different questions, and the chart rarely tells you which question it picked.