Cups to grams: why a cup of flour is not a cup of flour

6 minute read · updated 2026-10-31

Quick answer: One US cup of plain (all-purpose) flour weighs about 120 g, spooned in and levelled. A cup of granulated sugar is about 200 g and a cup of butter 227 g. A metric cup (250 ml) holds about 127 g of flour. The full table is below.

A cup is a measure of space. A gram is a measure of weight. That single difference is behind most of the confusion when a recipe asks for cups and your scales are sitting on the counter.

Fill a cup with flour and fill the same cup with honey. Both hold the same volume. One weighs about 120 g, the other about 340 g. Nothing has gone wrong. The cup has done its job both times. The ingredients simply have different densities, and density is what turns a volume into a weight.

Why flour is the worst offender

Flour is mostly air. How you get it into the cup decides how much air stays in there. Dip the cup straight into the bag and press down, and you compact the flour as you go. Spoon it in loosely and level the top with a knife, and you get far less. The gap between a packed cup and a lightly spooned cup can be 20 to 30 per cent, which on a cake is the difference between tender and tough.

This is the real argument for baking by weight. Scales do not care how you loaded the flour, whether the bag has settled in the cupboard, or how humid the kitchen is. A recipe written in grams gives the same cake in your kitchen as it did in the writer's. A recipe written in cups gives you their best guess at how you will scoop.

If you are stuck with cups and no scales, at least scoop the same way every time. Stir the flour in the bag to loosen it, spoon it into the cup without tapping or pressing, then level the top. Consistency is the next best thing to accuracy.

Not all cups are the same cup

The cup itself is not one fixed thing. A US cup is treated as 240 ml on food labels, although the US customary cup that most recipe weight charts are based on works out at 236.6 ml, and that is the cup Tantoo uses. An Australian cup is 250 ml, so an Australian recipe hands you about four per cent more of everything than a US one. That is harmless in a soup and noticeable in a sponge.

Pints are worse. An imperial pint is 568 ml and a US pint is 473 ml. If an old British recipe asks for a pint of milk and you pour a US pint, you are 95 ml short, which is close to a fifth of the liquid missing. The word is the same. The quantity is not. Where a recipe does not say which country it comes from, the spelling usually tells you: an American recipe will say all-purpose flour and baking soda, a British one plain flour and bicarbonate of soda.

How many grams in a cup?

These are the figures most recipe writers work with. Treat them as typical rather than exact, because brands, grinds and how firmly you pack the cup all move the number a little.

Look down that column and the point makes itself. Cocoa and oats are light and fluffy, so a cup of either weighs less than half a cup of butter. Honey is dense and heavy. Water is the convenient one, because a millilitre of water weighs a gram, which is why liquids are the only case where volume and weight line up neatly.

Following an American recipe in a British kitchen

A few habits make this painless.

• Buy digital scales that switch to grams and show single grams. They cost less than a cake tin and remove the problem at the source.
• Convert the dry ingredients to weight and leave the liquids in volume. A measuring jug is perfectly good for milk, water, oil and stock.
• Convert the whole recipe before you start. Write the grams next to each line. Doing sums with floury hands is how mistakes happen.
• Watch out for sticks of butter. One US stick is 113 g, which is half a cup. Four tablespoons is 57 g.
• Trust the dough, not the number. Flour absorbs different amounts of water depending on the brand and the weather, so hold back a little liquid and add it if the mix looks dry.

If you would rather not do the arithmetic, the kitchen section of Tantoo has a grams and cups converter and a recipe translator that will take a whole American method and give it back in grams, millilitres and Celsius. It is free, there is no account, and the work happens in your browser. There is more on dial settings and tin sizes in our guide to American recipes in a British kitchen.

The short version: a cup tells you how much room an ingredient takes up, and that is only loosely related to how much of it you are actually adding. Where precision matters, and in baking it usually does, weigh it.

Read next

• Cooking an American recipe in a British kitchen

  Cups, sticks of butter, Fahrenheit, gas marks, tin sizes and the ingredient names that mean something else here.

• Oven temperatures: Celsius, Fahrenheit, gas mark and fan

  A full conversion chart for oven settings, why fan ovens run hotter, and what to do with an air fryer.

• Baking tin sizes: how to swap tins without ruining a recipe

  Inch-to-centimetre tin sizes, how to scale a recipe to a bigger or smaller tin, and swapping round tins for square ones.

Open the Tantoo tools →

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