Buttermilk to Milk + Acid Converter
Make a quick buttermilk substitute from regular milk and an acid — lemon juice, vinegar or cream of tartar — with the exact amounts for any quantity you need.
How it works
Per cup of buttermilk: 1 tbsp lemon juice or vinegar + milk to the 1-cup line · or 1¾ tsp cream of tartar stirred into 1 cup milk
Buttermilk is prized in baking for its acidity, which tenderizes gluten and reacts with baking soda to give lift. You can mimic it by souring regular milk: add an acid, let it sit for 5–10 minutes, and it curdles slightly into a stand-in that behaves the same way in the batter. Lemon juice and vinegar are added by the tablespoon and topped with milk to the line, while cream of tartar is whisked directly into a full cup of milk.
Worked example
You need 2 cups of buttermilk. Using lemon juice, put 2 tablespoons of lemon juice in a measuring cup, then add milk until it reaches the 2-cup line (about 30 tablespoons of milk). Stir and rest 5–10 minutes before mixing it into your batter.
Frequently asked questions
How long does the milk need to sit?
About 5 to 10 minutes at room temperature. The acid lowers the pH and lightly curdles the milk, giving you the tang and thickness of buttermilk. If it barely thickens, that is fine — the acidity is what matters for reacting with baking soda.
Lemon juice or vinegar — does it matter?
Both work equally well at 1 tablespoon per cup. White vinegar is flavor-neutral; lemon juice adds a faint citrus note. Cream of tartar is a good option if you have no liquid acid: whisk about 1¾ teaspoons into a full cup of milk.
Can I use a plant-based milk?
Yes. Soy and other higher-protein plant milks curdle and thicken best; add the same 1 tablespoon of acid per cup. Very thin or sweetened milks may not thicken much, but the acidity still provides the leavening reaction.
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