"Baking soda spreads, baking powder puffs," is the rule I learned in Home Ec class.
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A well-stocked pantry is not complete without a fresh box of baking soda and a container of baking powder, essential ingredients for baked goods. Both are chemical leavening agents—that is, they both break down in the presence of moisture or heat and release carbon dioxide bubbles. The gas bubbles are trapped by the starch in the batter or dough and cause the baked good to expand while in the oven. In other words, these simple ingredients are responsible for making your baked cakes, homemade breads, and holiday cookies light, porous, and fluffy. But what happens if, in the middle of mixing a recipe, you find yourself short of baking soda? Can you substitute baking powder for baking soda?

How Are Baking Soda and Baking Powder Different?

Baking soda, or sodium bicarbonate, is a quick-acting leavening agent used in baking. When baking soda (which is alkaline) is blended with moisture and an acidic ingredient such as yogurt, buttermilk, sour cream, molasses, or brown sugar, carbon dioxide bubbles result. These bubbles allow cakes, quick breads, muffins, biscuits, and cookies to rise and take on a light texture.

Baking powder contains baking soda plus another acid in powdered form, usually cream of tartar. You do not need to combine baking powder with an acidic ingredient for it to work; it can leaven dough all by itself. When a recipe calls for both baking soda and baking powder, two things happen: The baking soda balances out any acidic ingredients in the recipe, while the baking powder gives it the extra lift it needs in the oven. Baking soda also helps your baked goods brown better.

Can I Substitute Baking Soda for Baking Powder?

Yes, as long as there is enough of an acidic ingredient to make a reaction. For 1/2 teaspoon of baking soda, you need 1 cup of buttermilk or yogurt or 1 teaspoon lemon juice or vinegar to unleash its leavening power. Keep in mind that baking soda has three times the power of baking powder, so 1/3 teaspoon of baking soda is equivalent to 1 teaspoon of baking powder.

Can I Make My Own Baking Powder?

If baking powder is really the ingredient you need, don't despair. You can use the baking soda and cream of tartar in your cupboard to create homemade baking powder. You can make as much or as little as you like, mixing one part baking soda with two parts cream of tartar:

  • If you would like to make enough to store, combine 1/4 cup cream of tartar with 2 tablespoons baking soda and sift, three times, through a fine strainer into a small bowl. Optional: Add 2 tablespoons of corn starch to your mixture. This will help keep your baking powder dry, prolonging its shelf life. Store airtight at room temperature for no more than six months.
  • For just a teaspoon of baking powder, you can substitute 1/3 teaspoon of baking soda and 2/3 teaspoons of cream of tartar.

Can I Substitute Baking Powder for Baking Soda?

Using baking powder instead of baking soda is not recommended. Baking powder is a combination of baking soda and other ingredients, so it is difficult to give a straight conversion formula for this substitution. Baking soda is also much stronger than baking powder and, by trying to provide enough leavening, you may wind up with an unpleasant metallic, salty taste in the final baked product.

If you do decide to substitute baking powder for baking soda, triple the amount listed in the recipe. Reduce any salt in the recipe by at least half, and consider reducing or replacing any acidic ingredients such as lemon, vinegar, buttermilk, or yogurt to avoid too much tang in your dish.

How to Use Baking Soda

Baking soda is a strong leavening agent and it is important to always use the exact amount called for in the recipe. While not enough baking soda will give an inadequate rise and a heavy finished product, adding too much will cause baked goods to fall and leave a metallic, soapy taste behind. Recipes with too much baking soda can also over-brown.

Measure baking soda properly by dipping the measuring spoon into the container and scooping out more than you need. Level off what's in the spoon with the flat edge of a table knife.

Always mix baking soda with a recipe's other dry ingredients before adding any liquid; it will start working as soon as it is wet.