Why a cup of flour and a cup of honey are not the same weight
A cup is a volume, a gram is a weight, and the bridge between them is density. Here is what a cup of each common baking ingredient actually weighs.
Published
There is no single answer to “how many grams is a cup”. A cup of cocoa powder is 84 g. A cup of honey is 340 g. That is a four-fold difference between two things measured with the same cup.
Volume versus weight
A cup measures how much space something takes up. A gram measures how much matter is in it. The bridge between them is density:
grams = millilitres × densityA US customary cup is 236.588 mL. So for any ingredient:
grams per cup = 236.588 × density (g/mL)Water has a density of 1 g/mL, which is why a cup of water is a tidy 237 g. Everything else is heavier or lighter than water, and the cup measurement follows.
What a cup actually weighs
| Ingredient | Grams per US cup | Density (g/mL) |
|---|---|---|
| Cocoa powder | 84 | 0.36 |
| Rolled oats | 90 | 0.38 |
| Almond flour | 96 | 0.41 |
| Cake flour | 113 | 0.48 |
| Powdered sugar | 113 | 0.48 |
| All-purpose flour | 120 | 0.51 |
| Granulated sugar | 198 | 0.84 |
| Rice (uncooked) | 195 | 0.82 |
| Brown sugar (packed) | 213 | 0.90 |
| Olive oil | 216 | 0.91 |
| Butter | 227 | 0.96 |
| Water | 237 | 1.00 |
| Milk | 245 | 1.04 |
| Honey | 340 | 1.44 |
Flour is the problem child
Flour is where cup measuring does the most damage, because it compresses. The same cup can hold anywhere from about 120 g to 145 g depending on how you fill it:
- Spoon and level — spoon flour into the cup, sweep flat. About 120 g.
- Scoop from the bag — the cup packs the flour as it goes in. Up to 145 g.
That is a swing of roughly 20%. In a cake recipe calling for three cups, the scooping method can add most of an extra half-cup of flour, which is the difference between tender and rubbery.
Granulated sugar has hard crystals that do not compress, which is why sugar measures reliably by volume and flour does not.
Cups are not even one size
Three different cups are in common use:
- US customary — 236.588 mL. What US recipes mean.
- US legal — 240 mL. What US nutrition labels use.
- Metric — 250 mL. Australian and most metric recipes.
A metric cup is about 6% bigger than a US customary one. For one cup of sugar that is roughly 10 g — usually survivable. Across a large bake, it is not.
The practical advice
Weigh things. A cheap digital scale removes every one of these variables at once, which is why no professional bakery measures flour in cups.
When you cannot weigh, at least be consistent: always spoon and level, and know which cup standard your recipe assumes.
Convert without the arithmetic
The kitchen converter does this with real densities and lets you pick your cup standard. There are also per-ingredient pages with full charts — flour, granulated sugar, butter and honey among them.