Buttermilk Substitute Calculator
A tablespoon of vinegar and enough milk to make a cup is the classic answer, and for most baking it works. Enter how much your recipe needs for the exact amounts, and see which substitutes come closest to the real thing — and where none of them do.
Enter your amount and press Calculate.
The acid is doing the work, not the tang
Buttermilk is acidic, and that acidity is what sets off baking soda. Swap in plain milk and King Arthur’s test bakes came out darker and denser, with pancakes that rose less. Adding a tablespoon of vinegar or lemon juice restores the reaction, which is the whole point of the substitute.
What it does not restore is flavour. Real buttermilk is cultured, and fermentation builds a complexity that souring milk for ten minutes does not.
Which milk, and how long to wait
Any fat level works — King Arthur ran their tests with 1% and skim, and Mississippi State Extension allows whole or skim. Plant milks work too, with the same tablespoon of acid; soy is closest to dairy on protein and body, oat a solid second.
Resting time is the one number sources genuinely split on: five minutes from America’s Test Kitchen and three Extension services, ten to fifteen from King Arthur, twenty from Mississippi State. Five to fifteen covers the credible range, and the mixture is ready when it thickens slightly and looks curdled.
Where the substitute falls short
King Arthur’s rule is a good one: the shorter the ingredient list, the less well a substitute performs. In a spiced cake nobody will notice; in a plain biscuit, the tang is half the recipe.
The bigger gap is thickness. Cultured buttermilk is viscous, and that body is what makes dressings cling and breading stick to fried chicken. Soured milk is thin. For dressings, marinades and fried-chicken brines, use real buttermilk, thinned yogurt or kefir instead.
What you are actually drinking
A cup of cultured low-fat buttermilk is 98 calories, 8.1 g of protein and 284 mg of calcium. Your substitute has the nutrition of whatever milk you made it from — souring milk with vinegar does not turn it into buttermilk in any nutritional sense, whatever it does for the recipe.
Sources
USDA FoodData Central · King Arthur Baking, how to substitute for buttermilk · America’s Test Kitchen, sour milk · Utah State University Extension, ingredient substitutions · Mississippi State University Extension, substitutions and equivalents
What the result tells you
Exactly what to mix for the amount your recipe calls for. Buttermilk is in the recipe for its acidity, which is what sets off baking soda — the substitute reproduces that, not the fermented flavour.
How to use it
Measure the acid into the cup first, top up with milk to the line, and leave it five to fifteen minutes until it thickens slightly and looks curdled. With cream of tartar, dissolve it in a splash of milk first or it clumps. Yogurt and kefir need no resting at all.
Recommendations
Any milk fat level works — King Arthur ran their tests with 1% and skim. Greek yogurt thinned with milk, one part to two, came closest to real buttermilk in their side-by-side bakes; kefir is closest overall because it is genuinely cultured. Plant milks work with the same tablespoon of acid, and soy is the nearest match to dairy on protein and body.
Health & wellbeing
A cup of cultured low-fat buttermilk is 98 calories, 8.1 g of protein and 284 mg of calcium. Your substitute has the nutrition of whatever milk you made it from — souring milk with vinegar does not turn it into buttermilk in any nutritional sense, whatever it does for the recipe.
Troubleshooting
Mixture did not curdle? Give it the full fifteen minutes; ultra-pasteurised and plant milks are slower. Biscuits tasted flat? The tang is the thing a substitute cannot fake, and the shorter the ingredient list the more that shows. Breading sliding off fried chicken? Soured milk is too thin — that job needs real buttermilk, thinned yogurt or kefir.
How it’s calculated
Ratios come from King Arthur Baking, America's Test Kitchen and the Cooperative Extension services of Utah State, Illinois, Colorado State and Mississippi State. Sources differ on resting time — five minutes, ten to fifteen, twenty — so the calculator gives the range rather than a single figure, and flags that America's Test Kitchen alone calls for one and a half tablespoons of lemon juice where everyone else says one. Nutrition is USDA FoodData Central.
Common questions
How do you make buttermilk with vinegar?
Put one tablespoon of white vinegar in a measuring cup, top up with milk to the one-cup line, stir, and leave it five to fifteen minutes until it thickens slightly and curdles. Any fat level of milk works. Lemon juice does the same job.
Is buttermilk substitute as good as real buttermilk?
For the chemistry, yes — the acid activates baking soda, which is the job buttermilk was doing. For flavour, no. Real buttermilk is cultured, and King Arthur's rule holds: the shorter the ingredient list, the more the difference shows. In a plain biscuit you will taste it; in a spiced cake you will not.
Can I use yogurt instead of buttermilk?
Plain yogurt goes in cup for cup, straight. Greek yogurt is too thick — thin it with milk, one part yogurt to two parts milk. That combination was the best stand-in in King Arthur's own tests.
Can I make buttermilk with almond or oat milk?
Yes — one tablespoon of lemon juice or vinegar, topped up with any plant milk to one cup, left about fifteen minutes. Soy is the closest to dairy on protein and body; oat is a solid second.