Why bakers weigh their flour (and how to convert cups when you can't)

Ask a baker for one tip and there's a good chance it'll be "buy a digital scale". Here's why.

A cup measures space, not flour

A cup is a volume: in the US, 236.6 ml. How much flour fits in that space depends on how you get it in there.

• Spooned and levelled: you spoon flour into the cup and sweep the top flat. About 125 g of all-purpose flour.
• Scooped: you dig the cup into the bag. The flour packs down, and you get 140 g or more.
• Sifted: aerated flour is lighter. About 115 g.

That's up to a 20% difference in the main ingredient of a cake, from the same recipe. Too much flour is the most common reason for a dry, dense bake.

Different ingredients, different weights

Even measured the same way, a cup of one ingredient weighs very little like a cup of another. A cup of granulated sugar is about 200 g; a cup of powdered sugar (icing sugar) about 120 g; a cup of rolled oats only about 80 g. There's no single "cups to grams" number, so a converter has to know the ingredient.

Cups around the world

Not every cup is the same size, either. Australia, New Zealand and Canada use a 250 ml metric cup, which holds about 6% more than a US cup. If a recipe is from one of those countries, convert with a metric cup.

Convert any cup measure

Type the amount, choose the ingredient and how it was measured, and get the weight in grams:

Worth buying a cheap scale

You don't need to weigh everything. Soups, stews and stir-fries are forgiving. But for cakes, bread and pastry, a cheap digital scale makes a recipe come out the same every time, and saves on washing up too: you can weigh everything straight into one bowl.