Why is there no single cups-to-grams number?

A cup measures volume — the space something takes up. A gram measures weight. How much a given volume weighs depends entirely on what it is: a cup of flour is about 125 g, a cup of honey about 340 g.

Why do flour measurements vary so much?

Flour compacts. Scooping the cup straight into the bag packs it down and can add 20% over spooning it in and levelling off. Recipes generally assume the spooned-and-levelled method.

Kitchen

Cups to grams converter

Cups to grams and back, per ingredient — because a cup of flour and a cup of honey weigh very different amounts.

Ingredient

Direction

Cups

cup

All-purpose flour

125 g

1 cup of all-purpose flour weighs about 125 g.

Per cup: 125 g
Per tablespoon: 7.8 g
Per teaspoon: 2.6 g
Per 100 ml: 53 g

Common amounts

¼ cup: 31 g
⅓ cup: 42 g
½ cup: 63 g
⅔ cup: 83 g
¾ cup: 94 g
1 cup: 125 g
1 ½ cup: 188 g
2 cup: 250 g

Spooned into the cup and levelled. Scooping straight from the bag can add 20% more. These densities are approximations — published charts differ by a few grams. For baking, where ratios matter, weighing is more reliable than any cup measurement.

Questions

Why is there no single cups-to-grams number?: A cup measures volume — the space something takes up. A gram measures weight. How much a given volume weighs depends entirely on what it is: a cup of flour is about 125 g, a cup of honey about 340 g.
Why do flour measurements vary so much?: Flour compacts. Scooping the cup straight into the bag packs it down and can add 20% over spooning it in and levelling off. Recipes generally assume the spooned-and-levelled method.