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Baking measurements: cups, grams, ounces and tin sizes

Baking is the one kitchen task where measurement error shows up in the result. A cup of flour can weigh anywhere between 120 and 150 grams depending on how it was filled, which is enough to turn a tender crumb dry. This guide explains why volume measures fail for dry goods and how to convert American recipes reliably.

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Volume versus weight, and why bakers pick weight

A cup measures volume, so what it holds depends on density and on packing. Scooped straight from the bag, flour compacts and a US cup can hold 150 grams. Spooned in and levelled, the same cup holds about 120 grams. That 25 per cent swing is invisible while you work and unmissable when the cake comes out.

Weight has no such ambiguity. One hundred grams of flour is one hundred grams however it got into the bowl, which is why professional recipes and every European cookbook use grams. Digital scales that read to one gram cost very little and remove the problem entirely.

Tin size is the second common trap, and it is a genuine unit conversion. American recipes specify inches, European tins are sold in centimetres, and the relationship is area rather than length. A 9-inch round tin is 22.9 cm and holds noticeably more than a 20 cm tin — about 30 per cent more batter — so the same mixture bakes shallower and faster.

Key facts

Flour varies wildly

A US cup of plain flour ranges from 120 g spooned to 150 g scooped.

Stable staples

Granulated sugar is about 200 g per cup and water 237 g, because neither compacts much.

Two different cups

A US cup is 236.6 ml; a metric cup is 250 ml — a six per cent difference.

Ounces are exact

One ounce is 28.3495 g, and one pound is 453.59 g.

Tins scale by area

A 9-inch tin is 22.9 cm and holds roughly 30 per cent more than a 20 cm tin.

Oven conversion

350°F is 177°C, normally set as 180°C on a European dial.

How to get it right

1

Weigh dry ingredients

Use grams for flour, sugar, cocoa and butter rather than cups.

2

Convert with the exact factor

Multiply ounces by 28.3495 and pounds by 453.59.

3

Check the tin

Convert inches to centimetres by multiplying by 2.54 before choosing your tin.

4

Adjust depth and time

If your tin is wider, the batter is shallower — start checking ten minutes early.

Questions people ask

About 125 g if spooned in and levelled, which is the convention most recipe writers assume. Scooped from the bag it can reach 150 g.

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