Baking Soda vs. Baking Powder: What's Actually the Difference
They're not interchangeable, and mixing them up can ruin a bake.
A clear explanation of the difference between baking soda and baking powder, when each one is used, and what happens when a recipe calls for the wrong one.
Baking soda and baking powder look almost identical sitting side by side in the pantry, but they behave very differently in a recipe, and mixing them up usually shows in the final result.
Baking Soda Needs an Acid to Work
Baking soda is pure sodium bicarbonate, and on its own it does nothing. It needs an acidic ingredient in the batter, like buttermilk, yogurt, brown sugar, or lemon juice, to react and produce the gas bubbles that make baked goods rise.
Baking Powder Already Has the Acid Built In
Baking powder is baking soda combined with a powdered acid and a bit of cornstarch. That means it can create lift on its own, without needing an acidic ingredient elsewhere in the recipe.
Why Recipes Sometimes Use Both
A recipe might call for baking soda to neutralize an acidic ingredient and improve browning, plus baking powder to provide the actual lift. It's not a mistake in the recipe, both are doing different jobs at once.
What Happens If You Swap Them
Using baking soda in place of baking powder, without an acid to activate it, usually leaves baked goods flat and can leave a bitter, metallic aftertaste. Using baking powder in place of baking soda can throw off the balance of a recipe that was relying on soda to react with its other ingredients.
How to Check If Yours Still Works
Baking soda and baking powder both lose potency over time. Drop a small spoonful of soda into vinegar, or powder into hot water, and if it fizzes energetically, it's still good. A weak reaction means it's time to replace it.