What’s the Difference Between Baking Soda vs. Baking Powder?

Baking soda is an alkaline compound that reacts with the acidity of other ingredients to produce carbon dioxide. To activate it, you need both a liquid and an acid. Acidic ingredients you might have on hand include lemon juice, yogurt, buttermilk, vinegar, brown sugar, and cream of tartar. When baking soda is activated, the carbon dioxide it produces is what leads baked goods to rise and become light and fluffy. One reason you may end up with a dense pastry is not using enough baking soda. The opposite isn’t true, though: too much baking soda won’t make a pastry extra fluffy, it can just make it taste bitter. Baking soda is sometimes referred to as sodium bicarbonate.

Unlike baking soda, baking powder already has an acid built in. All you need to do to trigger a reaction is add liquid. Most baking powder on the market is double-acting, meaning it makes a dish rise twice: once when it gets wet at room temperature, and again when it’s combined with heat in the oven. Single-acting baking powder, more common with professional chefs, only reacts when heated. Baking powder is used in recipes that don’t already call for acidic ingredients, like quick breads and many baked goods. In a basic biscuit recipe with just baking powder, eggs, milk, and flour, the baking powder reacts with the liquid and acts as the rising agent.

The short answer is: it depends on which one you’re missing.

Substituting Baking Powder for Baking Soda

If a recipe calls for baking soda and you only have baking powder, use about three times as much. For example, a recipe calling for 1 teaspoon of baking soda would need about 3 teaspoons of baking powder. Be mindful this formula isn’t perfect: too much baking powder can make a dish taste acidic and salty, and too little will leave it dense.

Substituting Baking Soda for Baking Powder

Because baking powder needs a liquid to react, swapping in baking soda alone won’t work. Instead, pair a small amount of baking soda with an acid. For each teaspoon of baking powder called for, try one of these combinations:
½ cup buttermilk or plain yogurt plus ¼ teaspoon baking soda
¼ teaspoon baking soda plus ½ teaspoon vinegar
½ teaspoon lemon or citrus juice plus ¼ teaspoon baking soda

Keep in mind that the added liquid can affect the consistency of your final dish, so adjust other liquids in the recipe accordingly.

Using Both Together

Some recipes call for both baking soda and baking powder. This usually happens when the recipe has acidic ingredients like lemon juice or buttermilk for flavor: using only baking soda would neutralize that flavor, but combining both leaves enough acid to keep the tang while still getting a full rise. The combination can also help baked goods brown better, since browning happens more readily in an alkaline environment.

If you don’t have baking powder on hand, whipped egg whites can work: whip them with a hand or electric mixer until soft peaks form, then gently fold them into the batter. Club soda can also substitute for baking powder if used to replace another liquid, like milk, in the recipe, though it may water down the final dish.

Both baking soda and baking powder lose their effectiveness over time. Unopened, baking powder will stay fresh for 18 months. Once opened, its shelf life will depend on how much moisture (humidity) it is exposed to, but it will typically last three to six months. Unopened baking soda will be effective for about two years. Once it’s opened, it lasts about six months.

Both baking powder and baking soda should be stored in a cool, dry place.

Baking soda has plenty of uses outside of baking, especially as a deodorizer. Sprinkling some in a cat’s litter box or at the bottom of your trash can helps reduce odors, and keeping an open container in the fridge helps absorb them too. Baking soda also works as a mild cleaning agent, like on countertops and sinks. Chef Francis Mallmann keeps a well-stocked pantry of kitchen staples like this in his own Tuscan kitchen.