How to Test Baking Soda and Baking Powder (And What's the Difference?)
Flat cookies. Dense muffins. A cake that didn't rise. Nine times out of ten, it's the leavener. Here's how to know before you bake.
How to Test Baking Soda
Add ¼ teaspoon of baking soda to 2 teaspoons of white vinegar, or to hot water with a splash of vinegar stirred in. You'll see the result instantly: if it bubbles vigorously and foams up, your baking soda is still good. Weak fizz or no reaction at all means it's lost its strength. Toss it and open a new box.
How to Test Baking Powder
Add 1 teaspoon of baking powder to ½ cup of hot water. Strong, immediate bubbles mean it's still active and ready to lift your batter. If you barely see a reaction, replace it — flat baked goods are guaranteed otherwise.
Baking Soda vs. Baking Powder: What's the Difference?
They look almost identical, but they work differently. Baking soda is pure sodium bicarbonate. It needs an acid, like buttermilk, yogurt, lemon juice, vinegar, brown sugar, or cocoa, to react and release the carbon dioxide that lifts your batter.
Baking powder already contains baking soda plus a dry acid (and a little cornstarch to keep them apart). It activates when it hits moisture and again when it hits heat, which is why most modern baking powders are labeled "double-acting."
Because they work differently, they aren't interchangeable without adjusting the rest of the recipe.
How Long Do They Last?
Baking soda: roughly 6 months to 1 year once opened. An unopened box keeps for about 2 years.
Baking powder: 6 to 12 months once opened, up to about 18 months unopened.
Both last longer if you store them in a cool, dry place with the lid tightly closed. Heat and humidity are the enemies — keep them out of the cabinet right above the stove.
Can You Substitute One for the Other?
Yes, with adjustments. To replace 1 teaspoon of baking powder, use about ¼ teaspoon of baking soda plus an acidic ingredient already in (or added to) your recipe — buttermilk, yogurt, lemon juice or vinegar all work. Going the other way is trickier and rarely worth it.
Expect a slightly different flavor when you swap: too much baking soda without enough acid leaves a soapy, metallic aftertaste, while baking powder tends to be more neutral.
Scaling a recipe? Adjust every ingredient automatically →