Baking Soda and Buttermilk for Baking Powder (Biscuits)

Swap 1/4 teaspoon of baking soda and 1/2 cup of buttermilk for each teaspoon of baking powder, then see the math in a drop biscuit recipe with grams, a liquid check and sodium per biscuit.

Most baking powder swaps stop at one line: 1/2 cup of buttermilk and 1/4 teaspoon of soda per teaspoon. That line is correct as far as it goes. It leaves out the part that wrecks a recipe, which is where the extra liquid goes.

This page shows the swap inside a real recipe, soda-only buttermilk drop biscuits. It is our adaptation and it is untested: the ratios come from the sources below, and the full formula has not been baked here. For the wider list of swaps, see baking soda instead of baking powder and baking soda replacement.

Why the buttermilk replaces the liquid, not adds to it

Both Healthline and Betty Crocker say to cut the other liquid by the amount of buttermilk you add. In a biscuit there is no other liquid to cut. The buttermilk is the whole liquid, so it is also the acid. Count it as the liquid and set the soda by the cup of buttermilk, not by the teaspoon of powder you removed.

Here is our worked example. King Arthur's buttermilk biscuits use 3 cups (360 g) of flour and 1 tablespoon of baking powder, which is 3 teaspoons. Apply the per-teaspoon swap three times and you need 1 1/2 cups of buttermilk and 3/4 teaspoon of soda. King Arthur's dough takes 227 to 255 g of liquid, so the swap on its own overshoots the dough and turns it wet. Scale the card down to 2 cups of flour and the numbers land at 1 cup of buttermilk and 1/2 teaspoon of soda, and those agree with Bake School's per-cup rules.

The Food Science / Lab Kitchen Note

Except where a source is named, this section is standard food chemistry.

Baking soda is sodium bicarbonate, a base. Buttermilk is acidic. When the two meet, the acid and the bicarbonate react and release carbon dioxide, and that gas is what lifts the dough. The reaction starts on contact, which is why this page keeps saying to bake at once.

Baking powder works differently. It carries its own acid with the bicarbonate, and the double-acting kind releases gas twice, once when wet and again in the oven. Soda and buttermilk give you one reaction only, and most of it happens in the bowl. So the dough has less in reserve if it waits.

The soda amount has to match the acid. Too little soda leaves some of the acid unreacted. Too much leaves bicarbonate that has nothing to react with. Bake School describes that leftover soda as tasting soapy, and says more soda browns the crust faster because a higher pH speeds the Maillard reaction. Its bakes with extra soda came out flatter with a more open crumb. That was a baker's test, not a controlled study.

Why 1/2 teaspoon per cup of buttermilk? Kitchen Savvy and Bake School both give about that amount when the recipe has no other acid. If molasses or natural cocoa is in the mix, Kitchen Savvy says it needs more soda. Our biscuits have flour, butter, salt and buttermilk, so the plain figure applies.

Three leaveners compared

This table compares published data and our card, not finished bakes. Where no source gives a figure, the cell says so.

The Arm and Hammer row uses twice the soda of our card for the same 2 cups of flour, but it adds cream of tartar as a second acid and an egg. We did not try to reconcile the two formulas, so take all numbers for one recipe from one source.

Common mistakes

Adding the buttermilk on top of the usual liquid. The sources say to cut the other liquid by the buttermilk. In this recipe there is no other liquid, so the buttermilk is the entire amount. Adding milk as well makes the dough wet and slack.

Letting the dough wait. The reaction starts on contact, so a dough that sits has already spent part of its gas before the oven. Have the oven hot and the sheet lined first, mix the buttermilk in last, and scoop straight onto the sheet.

Adding extra soda to be safe. More soda does not mean more lift once the acid is used up. By Bake School's account it leaves a soapy edge and browns the crust faster. Measure the half teaspoon level, and weigh it if you have a scale that reads to a tenth of a gram.

Buttermilk alternatives and swaps

Sodium per biscuit

This is our own calculation from USDA FoodData Central. USDA lists baking soda at about 27,400 mg of sodium per 100 g and gives 2.3 g per 1/2 teaspoon, so the half teaspoon in the recipe holds about 630 mg. Table salt is 38,800 mg per 100 g, so 1/2 teaspoon (3 g) holds about 1,164 mg. Divide by 8 biscuits.

Per biscuit that is about 79 mg from the soda, 146 mg from the salt, 46 mg from the butter and 45 mg from the buttermilk. The flour adds about 1 mg. The total is about 317 mg, or 14% of the 2,300 mg FDA Daily Value.

On the weight of a teaspoon: this page uses 4.6 g per teaspoon, the USDA figure. Other pages on the site say 6 g per teaspoon, which is King Arthur's number. The two sources weigh a level teaspoon differently, so check which one a recipe is using before you compare sodium.

Storing and rewarming

The only storage text we found comes from King Arthur's baking powder biscuits: leftovers keep well wrapped at room temperature for several days, freeze for longer, and should be rewarmed before serving. No fridge time is sourced. That advice is for a different leavener, so treat it as a starting point for this soda-only version, which has not been baked here.

Where the numbers come from

Bake School is a baking guide with a baker's own tests. Its soda per cup of flour and per cup of buttermilk figures are presented as guidelines, and its soapy taste and browning notes came from the author's bakes, not a controlled study. King Arthur Baking is a specialist baking site, and its biscuit page supplies the flour weight, liquid range, oven temperature and time, and the storage line. Healthline and Betty Crocker supply the per-teaspoon swap, and Kitchen Savvy the soda per cup of buttermilk. Arm and Hammer's quick biscuit page is a soda-leavened precedent from the product's maker.

USDA FoodData Central is a nutrient database, and the FDA Daily Value is a regulatory reference. The sodium and nutrition are our own calculations from those figures. We found no study that compares these leavening swaps in a biscuit, and none is cited here. For another bread that leans on soda and buttermilk alone, see Irish soda bread, and for the difference between the two leaveners, see baking soda vs baking powder.