Baking Soda Instead of Baking Powder: Exact Swap Ratios

Yes, if you add an acid. Make a homemade baking powder from baking soda, cream of tartar and starch, with US and gram measures, liquid-acid swaps, sodium per use and storage.

Baking soda alone is a base. It can't lift a biscuit or a quick bread until something acidic gives it work to do, and that is the whole reason this swap needs a second ingredient. The fix is short, and you can do it with what's already in the kitchen.

This page is about a recipe that calls for baking powder when the pantry has only baking soda. For another baking soda recipe on the site, see soft pretzels with a baking soda bath or Irish soda bread.

The Food Science / Lab Kitchen Note

Here's why this works. According to an NC State news article that cites Prof. Keith Harris, baking soda is sodium bicarbonate, a base. When it meets an acid such as buttermilk, yogurt or vinegar, it releases bubbles of carbon dioxide, and it does so almost at once.

Baking powder is the same bicarbonate with its acids already packed in. The NC State piece names monocalcium phosphate, then sodium acid pyrophosphate or sodium aluminum sulfate, which makes it double acting: one burst when wet, a second under oven heat.

The homemade mix is simpler. Cream of tartar is the dry acid, and King Arthur's recipe adds starch. With only one acid in the jar, the mix is single-acting, which is why King Arthur says it's best in bakes that go straight into the oven.

Three ways to swap, compared

This table lists what the sources give, per 1 teaspoon of baking powder. It's a comparison of published data, not of finished bakes. The spoon measures are the sources' figures. The gram and ml column is separate because those equivalents are our own conversions (grams derived from King Arthur's batch weights, ml from standard volume equivalents), not published figures.

One caution on the middle row. Club House publishes a larger amount of the same liquid acid for the same baking soda, so the two sources disagree. This page uses the King Arthur figure and doesn't average the two. Pick one source for a given recipe and stay with it.

Cream of tartar isn't in every pantry. If yours lacks it, the other two rows are the sourced alternatives. Gluten-free versions of the mix have no sourced data here. On aluminum, NC State lists sodium aluminum sulfate among the acids in some store-bought baking powders, and the homemade mix (baking soda, cream of tartar and starch) doesn't contain it.

Common mistakes

Skipping the acid. Soda by itself has nothing to react with, so the bake doesn't get the bubbles that baking powder would have given it. Add the acid from one row of the table, never just a bit more soda.

Letting the batter sit. Soda and acid start working as soon as they're wet together. Mix the dry ingredients first, add the liquids last, and put the pan in the oven straight away.

Blending two sources. Using King Arthur's baking soda amount with Club House's liquid acid amount gives a ratio no source publishes. Take all the numbers from one source.

Make and store the homemade mix

The card above makes a batch of about 1/4 cup. King Arthur says it keeps in an airtight container at room temperature for up to 6 months. The liquid-acid and buttermilk swaps aren't stored: you measure them into the batter when you bake.

Before you trust any old jar of leavener, run the checks from King Arthur's 2015 article on testing freshness. Stir 1/2 teaspoon baking powder into 2 tablespoons warm water, and it should bubble clearly. Stir 1/2 teaspoon baking soda into 1 tablespoon vinegar, and it should fizz at once. Those checks are written for baking powder and baking soda. No source here applies them to the homemade mix.

Going the other way

The reverse swap is a different problem. King Arthur says to use 3 teaspoons of baking powder for 1 teaspoon of baking soda, and warns that this much powder may leave a slightly bitter, off-putting taste. Chowhound says the same direction can leave a metallic taste.

Where the numbers come from

Two references carry the chemistry. The NC State news article, which quotes Prof. Keith Harris, is a technical reference for how sodium bicarbonate reacts with acids and how double-acting powder is built. It's not a study, and it didn't test any bakes.

Three King Arthur pages supply the rest: the guide to baking soda and baking powder substitutions gives the per-teaspoon ratios and the reverse swap, the homemade baking powder recipe gives the batch weights and the 6-month storage, and the 2015 freshness article gives the checks. They're a baker's technical reference too, not studies, and we found no trial that compares the three swaps side by side. That's why the crumb, rise and taste cells above say "No sourced data."

Sodium per use

This one is our own calculation. USDA FoodData Central (SR Legacy) lists baking soda at 27,400 mg sodium per 100 g and cream of tartar at 52 mg per 100 g. With King Arthur's 14 g per tablespoon of baking soda, 1/4 teaspoon holds about 1.2 g (our conversion), or about 320 mg sodium. That's about 14% of the 2,300 mg FDA Daily Value. It's also what one 1-teaspoon use of the homemade mix gives you under our deduction above: about 321 mg once the cream of tartar is added. The starch isn't counted.

Tips for the swap

• Weigh the batch. The gram weights come straight from King Arthur's recipe, and a scale beats a heaped spoon.
• Whisk the powders well before jarring them, so a teaspoon from the top matches one from the bottom.
• Measure leavener level. More isn't better, and extra can taste off.

Store the mix in an airtight container at room temperature, and mix a fresh batch when the 6 months King Arthur gives are up.