Buttermilk brings two things to a recipe: tang and acid. The acid reacts with baking soda to lift pancakes, biscuits and quick breads, and it tenderises meat in marinades. Any swap has to supply that acid, or the bake will rise less and taste of soda.
Use one of these instead — amounts update as you change the quantity.
Best for: Pancakes, biscuits, cakes, fried chicken marinade
Stir and let it stand 5–10 minutes until it thickens slightly and curdles at the edges.
Best for: Quick breads, muffins, dressings
Closest in thickness and tang. Greek yogurt works too; thin it with a little extra milk.
Best for: Cakes, dips, dressings
Richer than buttermilk, so the crumb comes out a little more tender.
Best for: Baking only
Whisk the cream of tartar into a few spoonfuls of milk first so it does not clump.
Baking soda (sodium bicarbonate) is a base. When it meets an acid in a wet batter, it reacts and gives off carbon dioxide, and those bubbles expand in the oven's heat to lift the bake. With too little acid, unreacted soda stays behind: the crumb turns yellowish and the bake tastes soapy or metallic. With too much, you get less rise and a sharper tang.
That's why plain milk is a poor stand-in for buttermilk in a recipe leavened with soda. Drag the sliders to see the balance.
Balanced: the acid neutralises the soda, releasing carbon dioxide that lifts the batter with no off taste.
Rule of thumb: ½ tsp baking soda per 1 cup of buttermilk, yogurt or other acidic liquid. That's why every buttermilk swap on this site keeps the acid.
Only if you add acid. Plain milk has no acid to react with baking soda, so the bake will be flatter and can taste soapy. Add 1 tablespoon of lemon juice or vinegar per cup and wait 5 minutes.
About 5–10 minutes at room temperature. It will not get as thick as cultured buttermilk, but the acidity is what matters for baking.
Yes. Soy milk curdles best; oat and almond milk work but stay thinner.
Other swaps: Heavy cream · Baking powder · Egg · Cornstarch · Sour cream · Brown sugar · Butter · Milk