How Many Ml in a Cup? | The One Number Every Cook Needs

A US customary cup holds 237 mL, while the US legal cup used for nutrition labels holds 240 mL. Knowing which one your recipe uses is the difference between a perfect bake and a flop.

You’re standing at the counter with a cup measure and a liquid measuring cup, staring at a European blog’s recipe in milliliters. You need the answer to “how many ml in a cup?” — but it’s not one single number. The cup you grab and the country the recipe came from both matter. Here is the exact breakdown for US cooks, with the conversions that actually come up in a real kitchen.

The Three Cups You’ll Actually Encounter

The reason the ratio isn’t a single number is that “a cup” means three different things depending on context. The US customary cup (what your Pyrex measuring cup uses for US recipes) is 237 mL. The US legal cup (used by food manufacturers on Nutrition Facts labels) is exactly 240 mL. The metric cup common in Australia and New Zealand is 250 mL. That last one is about 6% bigger than the US customary cup — enough to turn a tender cake into a dense one.

For day-to-day cooking, most US home cooks can treat 1 cup as 237 mL and never worry. For nutrition labels, you’ll see 240 mL. The two are close enough that a splash of milk won’t break a recipe. But for baking, especially when scaling a recipe up, the small difference compounds.

Quick Conversions for Common Cup Sizes

Here are the numbers you’ll reach for most often. The first column uses the standard US customary value of 237 mL per cup, rounded to the nearest whole mL.

The mental shortcut that works for most kitchens: 1 cup ≈ 240 mL. That single number handles both the customary and legal definitions without a calculator, and the 1% error is invisible in soups, sauces, and even most batters.

When the Small Differences Actually Matter

The two big traps are recipe origin and measuring method. If you’re following a recipe that originated in Australia, New Zealand, or Canada, their “1 cup” is 250 mL — 237 mL will leave you short by a noticeable margin. The same goes for older UK cookbooks that may use the imperial cup of 284 mL, though that standard is effectively retired.

Volume vs. weight is a deeper issue. A cup measures volume, not weight. One cup of water weighs about 240 grams; one cup of all-purpose flour weighs about 120 grams. That’s why professional bakers weigh flour by grams. If you’re baking a recipe that gives both cup and milliliter measurements, using the milliliter value when you can is more precise than scooping flour into a cup. If precision matters, the Wikipedia definition of the cup unit covers the full historical table and the exact legal definitions.

One more common slip: never use a drinking cup as a measuring cup. “One cup” in a recipe is a specific 8-ounce measuring cup, not whatever mug you grab from the cabinet. Drinking cups vary from 250 mL to over 350 mL, and using one will throw off the ratio of every recipe.

FAQs

Is 1 cup exactly 250 mL?

Not for US recipes. The metric cup used in Australia, Canada, and New Zealand is exactly 250 mL, but the US customary cup is 237 mL. If a recipe doesn’t say where it’s from, a US cook should default to 237 mL, though 240 mL is close enough for most dishes.

Why does my blender’s cup say 240 mL if recipes use 237?

Your blender’s markings follow the US legal cup definition of 240 mL, which is set by the FDA for nutrition labeling. Kitchen equipment sometimes rounds to this number because it’s a cleaner whole value. The 3 mL difference between 237 and 240 is negligible for everything except exact scientific measurement.

Do I need to worry about the 237 vs. 240 difference when baking?

For a single cup of liquid, the difference is about 1% — roughly half a teaspoon. That won’t break a cake. The risk comes from multiplying that small error across several cups in a large batch. If you’re scaling a recipe by 4x or more, use a scale and weight measurements instead of volume.