Densities of common ingredients
| Ingredient | Density | 100 g occupies |
|---|---|---|
| Water | 1.00 g/ml | 100 ml |
| Milk | 1.03 g/ml | 97 ml |
| Honey | 1.42 g/ml | 70 ml |
| Vegetable oil | 0.92 g/ml | 109 ml |
| Granulated sugar | 0.85 g/ml | 118 ml |
| Flour | 0.55 g/ml | 182 ml |
Frequently asked questions
Why does flour take up so much volume?
Because unpacked flour holds a lot of air between its particles: its bulk density is around 0.55 g/ml. It is also why the same cup of flour can weigh noticeably more once packed, which makes weighing more reliable than measuring by volume in baking.
How much is a US cup?
The standard US cup is 240 ml. It measures volume, not weight: a cup of flour weighs about 130 g, a cup of sugar 200 g, a cup of water 240 g.
Is the cup that comes with a rice cooker a real cup?
No, and it is the most common mistake with Japanese and Korean cookers. That plastic cup holds 180 ml, the go, an old Japanese measure equal to one tenth of a sho, and about 150 g of uncooked rice. The water lines inside the bowl are graduated for it, so filling it with a 240 ml American cup adds a third too much rice and the marks no longer mean anything. Measure the rice with the supplied cup, or weigh it.
Why does the same spoon of salt weigh so differently?
Because the crystal, not the salt, sets the volume. A level teaspoon holds about 6 g of fine table salt, about 4.8 g of Morton kosher salt and about 2.8 g of Diamond Crystal kosher salt, whose hollow flakes pack badly. A recipe written for one and made with another is out by a factor of two on the seasoning. American recipes that care name the brand; otherwise weigh, or taste before serving.
Are all eggs the same size in a recipe?
No, and four eggs are where it shows. European grading, in shell: small under 53 g, medium 53 to 63, large 63 to 73, extra large above. American large is graded by the dozen, 24 ounces, so about 57 g in shell and 50 g without, between the European medium and large. Four extra large eggs bring about 40 g more liquid than four medium ones, enough to loosen a batter. A recipe that does not say assumes large.
A cup is not a cup
The US legal cup is 240 millilitres, the US customary cup 236.588, the metric cup used in Australia and parts of Europe 250, and the Japanese cup 200. A recipe calling for four cups of milk therefore spans 800 to 1000 millilitres depending on where its author lives. The tablespoon fares no better: fifteen millilitres almost everywhere, but twenty in Australia, which throws any yeast or salt measurement out by a third.
The real trap is not capacity, though, it is density. A cup of flour weighs between 120 and 150 grams depending on whether it was spooned in or scooped straight from the bag, a twenty-five per cent spread on the ingredient that gives the dough its structure. Icing sugar, cocoa and wholemeal flour each behave differently again. That is why professional baking weighs everything in grams and measures only liquids by volume.