Ounces of Peanut Butter to Cups

Why a cup of peanut butter doesn't always weigh the same

Volume measurements are forgiving in some ways and brutal in others. A cup of peanut butter 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 (1.083 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 USDA: 1 cup = 256g. Smooth, full-fat.

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 peanut butter by its density (1.083 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.