One to one. That is the whole answer: kefir replaces buttermilk by
volume in almost any bake, with no other change. It works because the recipe is not really
asking for buttermilk — it is asking for acidic cultured milk, and kefir is that.
Why the ratio holds
Buttermilk does two jobs in baking. It reacts with baking soda to produce lift, and its
acidity tenderises gluten so the crumb stays soft. Kefir does both, at a comparable acidity.
Nothing else in the recipe is load-bearing.
When to nudge it
| Bake | Adjustment |
|---|---|
| Pancakes, waffles, soda bread | None |
| Muffins and quick breads | None |
| Thick batters | Kefir is thinner — hold back 1–2 tbsp |
| Delicate cakes | Kefir is sharper — a pinch more sugar |
| Marinades | None; kefir is arguably better |
The number that must not move
Half a teaspoon of baking soda per 250 ml of cultured milk.
This one is not flexible in the way the milk is.
More soda does not mean more rise. Past that ratio there is nothing left for the acid to
react with, and the excess simply tastes of itself — a soapy note and a yellowish crumb.
If your recipe uses baking powder rather than soda, no change at all is needed:
powder brings its own acid.
Going the other way
Buttermilk for kefir works too and comes out milder. Plain yogurt also substitutes if you
thin it — roughly three parts yogurt to one part milk gets you kefir’s consistency.
Frozen kefir is fine here
Thawed kefir separates
badly and is unpleasant to drink, and in batter that makes no difference whatsoever.
It disperses into flour even more readily than fresh.
Nearby:
What is kefir ·
What is ryazhanka ·
Raspberry Jam Doughnuts ·
Why dough does not rise