How to convert buttermilk
Our reference is 227 grams per US reference cup of buttermilk, liquid cultured buttermilk. That works out to about 0.9595 grams per millilitre, so cups = grams ÷ 227 and grams = cups × 227 in US customary measures.
For metric and Australian recipes the cup holds 250 ml, so one cup of buttermilk is about 239.87 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 buttermilk as: liquid cultured buttermilk. 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 cup as 227 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 26, 2026.