Buttermilk Substitute Calculator

How this works

Buttermilk's tang and thickness come from lactic acid. Adding an acid (lemon juice or white vinegar) to regular milk causes the milk proteins to curdle slightly, mimicking both buttermilk's tartness and its thickened texture closely enough for baking. Thinned yogurt works the same way since yogurt is already cultured and acidic. Cream of tartar is a dry acid that does the same job without adding extra liquid.

Source: The milk-plus-acid ratio is the standard substitution published by King Arthur Baking and most U.S. test kitchens.