How to convert peanut butter
Our reference is 270 grams per US reference cup of peanut butter, smooth spoonable peanut butter; stir separated oil in first. That works out to about 1.1412 grams per millilitre, so cups = grams ÷ 270 and grams = cups × 270 in US customary measures.
For metric and Australian recipes the cup holds 250 ml, so one cup of peanut butter is about 285.31 grams. Australian tablespoons hold 20 ml rather than 15 ml, which the calculator handles when you pick that system.
Preparation changes the weight
The reference describes peanut butter as: smooth spoonable peanut butter; stir separated oil in first. A different form, such as sifted, packed, melted, chopped or cooked, can hold a different weight in the same cup and needs its own reference. When a recipe gives a gram amount, weigh that amount instead of converting.
Brand, moisture and how firmly the cup is filled all move the practical result. Treat the numbers here as recipe equivalents, not laboratory densities.
Where the number comes from
The reference comes from King Arthur Baking ingredient weight chart, which lists 1/2 cup as 135 grams. Published recipe weight, normalised to one reference cup. This site assigns the published cup weight to its adopted US reference cup of 236.5882365 ml; the source itself does not define an exact millilitre cup volume. Checked September 25, 2026.