Cups to grams: why there is no single answer
“How many grams are in a cup?” is one of the most searched kitchen questions, and the honest answer is: it depends on what is in the cup.
Volume versus weight
A cup measures how much space something takes up. A gram measures how heavy it is. Water is the easy case, because one milliliter of water weighs about one gram. A US cup is about 236.6 ml, so a cup of water weighs roughly 237 grams.
Most ingredients are lighter or heavier than water for the same volume. Flour is full of air, so a cup of it weighs about half as much as a cup of water. That is why a single cups-to-grams number cannot exist.
Typical weights for one US cup
These are common approximations. Real values vary with how you scoop and pack.
| Ingredient | Approximate weight |
|---|---|
| Water | 237 g |
| All-purpose flour | 120 to 125 g |
| Granulated sugar | 200 g |
| Butter | 227 g |
Why bakers prefer a scale
Scooping flour can change the weight of a cup by 20 percent or more, depending on whether you spoon it in or pack it down. Weighing gives the same result every time, which matters most in baking.
Useful conversions that do have exact answers
Conversions between two units of the same kind are exact, because they are definitions:
For the nutrition of a specific food per serving, see our nutrition facts section.