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Why a cup is not one cup everywhere

Cooking volumes are unusually inconsistent between countries, which is why recipes travel badly. A US cup is about 237 millilitres, a metric cup is 250, and an imperial cup used in older British recipes is about 284. A US tablespoon is roughly 15 millilitres while an Australian tablespoon is 20, a difference of a third that matters a great deal for baking powder or salt and very little for water.

The deeper issue is that volume is a poor way to measure solids at all. A cup of flour can vary by a fifth or more depending on whether it was scooped, spooned or sifted, and whether it settled in the bag โ€” which is why the same recipe can produce quite different results for two people following it exactly. This is the reason professional and most European baking recipes specify weight. Where precision matters, particularly in baking, converting to grams and using a scale removes the ambiguity entirely; for soups, stews and anything forgiving, volume is perfectly adequate.

Worked example

An American recipe asks for 3 cups of milk. A US cup is about 236.6 ml, so you need about 710 ml. If you used a metric 250 ml cup instead, you would pour 750 ml, about 40 ml (roughly 6%) too much. For a sauce that hardly matters; for a cake batter it can change the texture.

Dry ingredients are trickier. One cup of plain flour weighs roughly 120 to 130 g depending on how you fill the cup, while one cup of sugar is closer to 200 g. If a recipe gives grams, use a kitchen scale for the most reliable result.

Common mistakes to avoid

  • Assuming all cups are the same. US, metric and older UK recipes use different cup sizes.
  • Converting flour by volume when the recipe was written by weight.
  • Using a heaped spoon when the recipe means a level spoon. A heaped teaspoon can hold almost double.

Last reviewed: 5 November 2026 by the YogiCalc team ยท How we calculate and verify ยท Spotted an error? Tell us

Frequently asked questions

How many millilitres in a cup?

It depends on the origin of the recipe. A US cup is about 237 ml, a metric cup is 250 ml, and an older imperial cup is about 284 ml. Check where the recipe comes from before converting.

Why do my baking results vary with the same recipe?

Most likely flour measured by volume. A cup of flour can vary by a fifth depending on how it was filled, and that variation shows up directly in the texture of baked goods. Weighing removes it.

Is a tablespoon the same everywhere?

No. A US tablespoon is about 15 ml and an Australian one is 20 ml. The difference is significant for concentrated ingredients such as raising agents, salt and strong flavourings.

Should I convert to weight?

For baking, yes wherever possible, since it is far more consistent. For cooking where proportions are forgiving, volume measures are perfectly adequate and usually quicker.

How many ml is a tablespoon?

A metric tablespoon is 15 ml and a US tablespoon is about 14.8 ml, so for cooking they are effectively the same. An Australian tablespoon is 20 ml.

Is 1 cup of water the same weight as 1 cup of flour?

No. A US cup of water weighs about 237 g, but a cup of plain flour weighs only about 120 to 130 g because it is much less dense.