A Cup Is Not a Cup
A cup measures volume, not weight. We took nine ingredients a home baker reaches for every week and looked up what one cup of each actually weighs, using the King Arthur Baking Ingredient Weight Chart. The same one-cup scoop swings from 89 grams to 237 grams depending on what is in it.
What One Cup Actually Weighs
Grams per US cup, ranked heaviest to lightest. Water (measured by volume) and flour (the baking baseline) are highlighted; the rest are King Arthur chart weights.
Flour (baseline) Water (by volume) King Arthur weight
The Full Table
Sixteen tablespoons make one US cup, so grams per tablespoon is simply the cup weight divided by 16. The last column is each ingredient against a cup of all-purpose flour.
| Ingredient | g / cup | g / tbsp | vs. flour |
|---|---|---|---|
| Water / generic liquid | 237 | 14.8 | 1.97× heavier |
| Butter | 227 | 14.2 | 1.89× heavier |
| Milk | 227 | 14.2 | 1.89× heavier |
| Brown sugar (packed) | 213 | 13.3 | 1.77× heavier |
| Granulated sugar | 198 | 12.4 | 1.65× heavier |
| Rice (long grain, dry) | 198 | 12.4 | 1.65× heavier |
| All-purpose flour | 120 | 7.5 | — |
| Powdered sugar | 113 | 7.1 | 0.94× (lighter) |
| Oats (old-fashioned) | 89 | 5.6 | 0.74× (lighter) |
Water is defined by volume (1 cup = 236.588 mL, so ≈ 236.6 g). Every other weight is the King Arthur Baking Ingredient Weight Chart value.
The Two Sugars Trap
The biggest single surprise is that "sugar" is not one weight. A cup of granulated sugar is 198 g; a cup of powdered (confectioners) sugar is 113 g. Same word on the recipe, 75% apart on the scale. Powdered sugar is milled fine and holds air, so it fills a cup at far lower density. Swap one for the other by volume and a frosting or shortbread is off by a wide margin — swap by weight and it is exact.
Flour has the opposite failure mode: it compresses. The chart value is 120 g for a properly spooned-and-levelled cup, but scooping straight from the bag packs it to 150 g or more — a 25% overshoot that turns a tender crumb dense. This is the case bakers make for a kitchen scale, in one number.
Common Questions
How much does one cup of flour weigh in grams?
One US cup of all-purpose flour weighs about 120 grams (King Arthur Baking Ingredient Weight Chart). That is roughly 7.5 grams per level tablespoon. Scooping the cup straight from the bag packs the flour and can push a "cup" to 150 g or more — a 25% overshoot on the recipe.
Why does a cup of sugar weigh more than a cup of flour?
A cup of granulated sugar weighs about 198 g while a cup of all-purpose flour weighs about 120 g — sugar is roughly 65% heavier for the identical one-cup volume. The grains are denser and pack tighter, so the same volume holds more mass.
Is granulated sugar the same weight as powdered sugar?
No. A cup of granulated sugar is about 198 g but a cup of powdered (confectioners) sugar is only about 113 g — a 75% difference for two ingredients both labelled "sugar". Powdered sugar is milled fine and traps air, so it weighs far less by volume.
Does one cup always weigh the same amount?
No. A cup is a unit of volume, not weight. Across nine common baking ingredients the same one-cup volume ranges from 89 g (old-fashioned oats) to about 237 g (water) — a 2.66× spread. That is why weighing in grams is more reliable than measuring by the cup.
All of these weights are built into our Cooking Measurement Converter, which converts by ingredient rather than assuming every cup weighs the same — see cups of sugar to grams for the two-sugars case above.
- Source data: the King Arthur Baking Ingredient Weight Chart, grams per US cup — the exact table the cooking converter ships and a unit test enforces.
- Spread: heaviest cup ÷ lightest cup. Expected: 236.6 g (water) ÷ 89 g (oats) = 2.66×.
- Sugar gap: granulated (198 g) ÷ powdered (113 g) − 1. Expected: 75%.
- Per tablespoon: grams per cup ÷ 16 (16 tbsp = 1 US cup).
Every number on this page is arithmetic on that one chart. King Arthur Baking is credited only as the source of the ingredient weights; this post is not affiliated with or endorsed by them.