1 cup of all-purpose flour weighs 120 grams. This conversion is important for accurate baking because volume measurements like cups can vary based on how the flour is scooped or packed.
Flour is a dry ingredient that compacts easily. Spoon it lightly into a cup, and you might get 113 grams. Pack it down, and you could reach 128 grams. This inconsistency explains why professional bakers and serious home cooks prefer weighing ingredients by grams.
The U.S. Department of Agriculture defines a cup as 240 milliliters (ml) of volume. However, the density of flour varies. All-purpose flour typically falls between 0.45 and 0.60 grams per milliliter (g/ml). For consistency, most recipes assume 0.50 g/ml, resulting in 120 grams per cup.
For the most precise results, use a kitchen scale. Here's how:
If you don't have a scale, spoon flour into the cup until it overflows slightly, then level it off with a knife. This method reduces packing and provides a closer approximation to 120 grams.
Many home bakers dip the cup directly into the flour bag, which packs the flour and can add up to 20% more volume than intended. This mistake often leads to dense, heavy baked goods. Always spoon flour into the cup rather than scooping it out of the bag.
Another error is assuming all flours weigh the same. Whole wheat flour, for example, is denser than all-purpose flour and can weigh up to 136 grams per cup. Cake flour, however, is lighter and may weigh only 105 grams per cup. Always check the specific gravity of the flour you're using.
Recipes that rely on chemical reactions, such as those involving yeast or baking powder, require precise measurements. Too much flour can prevent proper rising, while too little can lead to a collapsed structure. Bread, cakes, and pastries are particularly sensitive to these variations.
I learned this the hard way when baking a delicate sponge cake. Using a packed cup of flour resulted in a dense, gummy texture. Switching to a kitchen scale and measuring by weight produced a light, airy cake with perfect crumb structure.
While 1 cup of all-purpose flour equals 120 grams, other common dry ingredients vary:
| Ingredient | Grams per Cup |
|---|---|
| All-purpose flour | 120g |
| Whole wheat flour | 136g |
| Cake flour | 105g |
| Powdered sugar | 120g |
| Brown sugar | 220g |
Grams provide consistency, especially in recipes developed with precise measurements. Many international recipes use metric measurements, making it easier to follow along without converting units., scales are faster and more accurate than measuring cups, saving time and reducing waste.