How to convert sourdough starter
Our reference is 227 grams per US reference cup of sourdough starter, ripe, fed wheat-flour starter at 100% hydration; stir down before measuring. 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 sourdough starter 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 sourdough starter as: ripe, fed wheat-flour starter at 100% hydration; stir down before measuring. 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. The source lists 227 to 241 g per cup depending on ripeness; this site uses the lower published figure of 227 g and shows the range on the ingredient page. 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.