Quick answer
For 1 cup buttermilk, a common emergency substitute is milk plus acid: place 1 tablespoon lemon juice or white vinegar in a measuring cup, then add milk to reach 1 cup. For many simple bakes, plain Greek yogurt thinned with milk or water to a buttermilk-like consistency can give a closer combination of tang and body.
Which substitute should you choose?
| Option | Starting amount | Best use |
|---|---|---|
| Milk + lemon juice/vinegar | 1 tbsp acid, then milk to 1 cup | Quick emergency replacement |
| Plain Greek yogurt + milk/water | Thin to buttermilk consistency; use 1 cup | Pancakes, muffins, cakes, biscuits |
| Plain yogurt | Thin if notably thicker than buttermilk | Recipes where body and tang matter |
| Unsweetened non-dairy milk + acid | 1 tbsp acid, then milk to 1 cup | Dairy-free bakes; results vary by milk |
Why acidity matters
Buttermilk is acidic. In recipes containing baking soda, that acidity participates in the acid-base reaction that produces carbon dioxide. Replacing buttermilk with a neutral liquid without considering the leavener can therefore change rise, flavor, and browning.
Does milk + vinegar become real buttermilk?
No. Acidified milk is a convenient baking substitute, not cultured buttermilk. It can provide acidity, but its flavor, viscosity, and composition are not identical. That is why thinned plain yogurt can perform especially well in some recipes.