Cups of Cornstarch to Grams

Why a cup of cornstarch doesn't always weigh the same

Volume measurements are forgiving in some ways and brutal in others. A cup of cornstarch can vary by 10-20% in weight depending on how it's measured: spooned vs scooped, packed vs loose, sifted vs unsifted. The density figure used here (0.541 g/mL) matches the most common published recipe conventions, but if you're after baking precision, weighing on a kitchen scale is more accurate than measuring by volume.

Sourced from King Arthur Baking: 1 cup = 128g. Spooned and leveled.

Volume vs weight in cooking

The American convention of measuring ingredients by volume (cups, tablespoons, teaspoons) is convenient but introduces variability that doesn't exist in weight-based recipes. Most professional bakers and bakeries weigh ingredients to within a gram because the structure of baked goods depends on precise ingredient ratios. For everyday cooking — soups, sauces, sautés — the volume-to-weight imprecision rarely matters. For baking that depends on rising or texture (cakes, breads, laminated doughs), it matters a lot.

The conversion

Multiplying the volume of cornstarch by its density (0.541 g/mL) gives the weight in grams. The calculator at the top of this page does the math automatically; the formula box above shows the resulting linear factor for the specific volume and weight units selected here.