Buttermilk substitute

What to use

Milk and lemon juice or white vinegar

Gluten-free
Nut-free
Egg-free

1 tbsp 15 ml lemon juice or white vinegar
15 tbsp 230 g milk

How: Stir together and rest 5 to 15 minutes, until it thickens slightly and looks curdled.
Best for: Cakes, muffins, quick breads, pancakes, waffles.
What changes: Acid is right, flavor is flatter than cultured buttermilk. Vinegar needs 5% acidity or more; bottled lemon juice works.
Skip it when: Ranch, dressings and cold soups, where buttermilk is the flavor.

Greek yogurt thinned with milk

Gluten-free
Nut-free
Egg-free

⅓ cup 76 g plain Greek yogurt
⅔ cup 165 g milk

How: Whisk until smooth. One part yogurt to two parts milk.
Best for: Biscuits and pancakes. It was the runner-up to real buttermilk in King Arthur's biscuit and pancake tests.
What changes: Tangy, with real body. Browns well.

Plain yogurt, thinned if thick

Gluten-free
Nut-free
Egg-free

1 cup 245 g plain yogurt

How: Use as is. Loosen a thick yogurt with a splash of milk.
Best for: Marinades, cakes, quick breads.
What changes: Thicker than buttermilk, so batters come out a touch denser.
Skip it when: Thin batters (crepes, popovers) unless you thin it.

Milk and cream of tartar

Gluten-free
Nut-free
Egg-free

1 ¾ tsp 8.5 ml cream of tartar
1 cup 245 g milk

How: Shake or whisk until the cream of tartar dissolves.
Best for: Cakes and quick breads when you have no lemon or vinegar.
What changes: Works as an acid. Flavor is flat, but in cake other ingredients cover it.
Skip it when: Biscuits, where King Arthur's testers found it tasted flat.

Unsweetened soy milk and lemon juice

Vegan
Dairy-free
Gluten-free
Nut-free
Egg-free

1 tbsp 15 ml lemon juice or white vinegar
15 tbsp 220 ml unsweetened soy milk

How: Stir and rest about 15 minutes.
Best for: Vegan and dairy-free cakes, muffins and pancakes.
What changes: Mild flavor. Thins out a little more than dairy buttermilk.
Skip it when: Soy allergy. Choose another unsweetened plant milk and expect a thinner result.

Powdered buttermilk and water

Gluten-free
Nut-free
Egg-free

¼ cup 59 ml dried buttermilk powder
1 cup 235 ml water

How: Whisk the powder into the water. Follow the package if it differs.
Best for: Baking, when you keep it in the pantry.
What changes: Rose well in King Arthur's tests, with less richness than the real thing.

Diet labels describe the ingredients as normally made. Check packages for gluten and allergens. Some refined sugar is filtered with bone char, which matters if you eat vegan.

Which swap for which job

Use	Pick	Why
Pancakes and biscuits	Greek yogurt thinned with milk	Closest to real buttermilk in King Arthur's tests.
Cakes and quick breads	Milk with lemon juice or vinegar	Every acidified option worked in cake, because the other ingredients mask the flavor.
Marinades	Plain yogurt	The acid tenderizes. Thin it so it coats.
Ranch, dressings, cold soups	Real cultured buttermilk	Flavor carries the dish, and substitutes taste flat.

Do not substitute here

Recipes that use baking soda. Plain milk alone. Without acid the soda has nothing to react with, so cakes bake darker and denser and pancakes rise less.
Fresh dressings and soups. Milk with vinegar. It tastes flat when nothing else is cooking in the dish.

Questions

Can I use plain milk instead of buttermilk?

Only in recipes that use baking powder and no baking soda, and expect a flatter taste. Where soda is the leavener, add an acid.

Does the milk have to curdle?

It should thicken slightly and look a little curdled after 5 to 15 minutes. That means the acid has done its work. It is not spoiled.

Can I freeze real buttermilk to avoid this?

Yes. Freeze it in portions. It may separate when it thaws, and it is still usable in baking.