Why Your Baking Goes Wrong: Cups Aren't a Measurement

You followed the recipe exactly. The cake came out dry. You did not do anything wrong, you used a cup.

Cups measure the wrong thing

A cup measures volume. A recipe needs mass. Those are the same thing only if density is constant, and it isn’t.

Here is what one US cup actually weighs, depending on what’s in it:

One cup of…	Weighs
Rolled oats	90 g
Cocoa powder	85 g
Icing sugar	120 g
Plain flour	125 g
Granulated sugar	200 g
Butter	227 g
Water	237 g
Honey	340 g

A cup of honey weighs nearly four times a cup of oats. Any conversion chart that tells you “1 cup = 240 g” without asking what’s in the cup is not a conversion, it’s a guess that happens to be right for water.

Flour is the real problem

Flour compresses. How you get it into the cup changes the answer by more than a quarter:

• Sifted: 110–115 g
• Spooned in and levelled: 120–125 g
• Scooped straight from the bag: 140–150 g

Most recipes assume spooned and levelled. Most people scoop, because it’s one action instead of six. That single difference puts roughly 20–25% more flour in your cake than the recipe intended.

In a cake, that’s the difference between moist and dry. In bread, it changes the hydration enough that the dough won’t come together properly. In pastry, it’s the difference between short and tough.

And it compounds. A recipe using three cups of flour, scooped, can contain the better part of an extra cup.

Cups aren’t even the same size

Assuming you’ve solved the density problem, there’s a second one: a cup is not a standard unit.

Measure	US	Metric (UK/AU/NZ)	Old imperial
Cup	240 ml	250 ml	284 ml
Tablespoon	15 ml	15 ml (AU: 20 ml)	17.7 ml
Teaspoon	5 ml	5 ml	5.9 ml
Fluid ounce	29.57 ml	28.41 ml	28.41 ml
Pint	473 ml	568 ml	568 ml

The Australian tablespoon is the quiet troublemaker, at 20 ml it’s a third larger than everyone else’s. Three tablespoons of baking powder in an Australian recipe made with a British spoon is a meaningfully different cake.

Ounces and fluid ounces are different units

Ounces measure weight. Fluid ounces measure volume. They coincide only for water, by coincidence of definition.

So “8 oz flour” means 227 g on a scale. “8 fl oz milk” means about 240 ml in a jug. Eight fluid ounces of honey weighs about 12 ounces.

Recipes rely on context to tell you which they mean, which works until it doesn’t, usually in an older recipe, or one that’s been retyped by someone who dropped the “fl”.

Why professional recipes use grams

Every serious baking book has switched to weight, and it isn’t snobbery.

It’s accurate. 125 g is 125 g regardless of how you get it into the bowl.

It’s faster. Put the bowl on the scale, press tare, add flour to 125, press tare, add sugar to 200. One bowl, no measuring cups, nothing to wash.

It scales cleanly. Multiplying 125 g by 1.5 is easy. Multiplying “one cup plus two tablespoons” by 1.5 is a puzzle.

It travels. A recipe in grams works in any country without conversion.

It makes ratios visible. Once you see that bread is roughly 500 g flour to 350 g water, you understand hydration as a concept rather than a set of instructions. Baker’s percentages only make sense by weight.

Fan ovens run hot

Separate problem, same category of quiet failure.

A fan circulates air, so heat reaches the food faster. The standard adjustment is 20°C lower than a conventional recipe states, or about 35°F. Or keep the temperature and cut the time by roughly 10%.

Description	Conventional °C	Fan °C	°F	Gas
Cool	140	120	275	1
Moderate	180	160	350	4
Moderately hot	190	170	375	5
Hot	200	180	400	6
Very hot	220	200	425	7

Most published recipes give conventional temperatures unless they say otherwise. Ignoring the adjustment is the usual reason biscuits brown outside while staying raw in the middle.

While we’re here: your oven lies. An oven thermometer commonly reveals a 15–20°C gap between the dial and reality, and most ovens have hot spots. One cheap thermometer explains a lot of previously mysterious failures.

The fix costs about the same as two failed cakes

Buy a digital kitchen scale. That’s the whole recommendation.

Keep the measuring cups for liquids and for things where precision genuinely doesn’t matter, a cup of stock, a handful of herbs. Use the scale for anything baked, where the ratios decide the outcome rather than merely influencing it.

The first time you weigh flour and realise you’d been adding an extra 25% for years, several previously baffling failures will suddenly make sense.