Why American Recipes Fail in a UK Kitchen

A recipe written in Ohio and cooked in Manchester can fail for reasons that have nothing to do with technique. Six common measurements mean different things in different countries, and three of the differences are large enough to ruin baking.

The one that ruins cakes: the cup

Cup	Millilitres
US customary	237
US legal (nutrition labels)	240
Metric (UK, Australia, NZ, Canada)	250
Japanese	200

A metric cup is 5.7% larger than an American one. Across a cake using four cups of flour, that is nearly a full extra US cup — the difference between a sponge and a brick.

Convert with the cups to ml converter, or better, see below.

The one that ruins bread: the tablespoon

Tablespoon	Millilitres
US	14.8
UK / metric	15
Australia	20

Most of the world is 15 ml, and the 1.4% gap against the US spoon genuinely does not matter.

Australia is the outlier and it matters a lot. An Australian tablespoon holds four teaspoons, not three. Following an Australian recipe with a US spoon leaves you 26% short on every spoonful — and on baking soda, salt or yeast, that is not a subtlety. Use the tablespoons to ml converter if the recipe's origin is unclear.

The one that confuses everyone: the ounce

There are two, they measure different things, and they share a name.

• Ounce (oz) is a weight: 28.35 g
• Fluid ounce (fl oz) is a volume: 29.6 ml in the US, 28.4 ml in the UK

They are close enough for water to be confused constantly, and wrong for everything else. 8 oz of flour is 227 g; 8 fl oz of flour is about 125 g — nearly half as much.

The rule: weight ounces for solids, fluid ounces for liquids. If a US recipe says "8 oz flour" it means weight. Convert with oz to grams for solids and oz to ml for liquids.

The pint, for completeness

A US pint is 473 ml; an imperial pint is 568 ml — 20% larger. It rarely appears in recipes but it appears constantly in serving sizes and drink recipes. See pints to ml.

Oven temperatures

°C = (°F − 32) × 5/9. Subtract first, then multiply — the other order is wrong by about 18 degrees.

°F	°C	Usually written
325	163	160
350	177	180
400	204	200
425	218	220
450	232	230

Converted oven temperatures are always rounded to the nearest 10°C by convention, so the Fahrenheit to Celsius converter gives the exact figure and the recipe gives the rounded one. Both are right.

Fan ovens run hotter. Reduce a conventional temperature by about 20°C for a fan oven — a 180°C recipe becomes 160°C fan. US recipes almost never say which they assume; most assume conventional.

The fix that makes all of this go away

Weigh things.

Cups measure volume, and for dry goods volume is not a reliable proxy for quantity. A cup of flour is anywhere from 120 g to 150 g depending on whether it was scooped or spooned, and how settled the bag was. That is a 25% swing on the main structural ingredient of most baking — larger than any of the national differences above.

American recipe writers increasingly publish gram weights alongside cups for exactly this reason. Where a recipe offers both, use the grams and ignore the cups entirely.

Cups are a perfectly good unit for liquids, where volume is exactly what you want. For flour, sugar, butter and anything else that compresses, a £10 scale removes an entire category of failure.