The short answer: no, you cannot swap them one-for-one

Baking soda and baking powder are both leavening agents — they make baked goods rise — but they work in completely different ways. If you replace baking soda with baking powder in a cookie recipe without adjusting anything else, your cookies will spread too much, taste metallic or soapy, and may not brown properly. The reverse problem happens if you use baking soda where baking powder is called for: your cookies will be dense and flat.

The reason comes down to chemistry. Baking soda is pure sodium bicarbonate. It needs an acid in the dough — buttermilk, brown sugar, lemon juice, cocoa powder, or molasses — to set up and create carbon dioxide bubbles when ready. Baking powder is baking soda plus acid (usually cream of tartar) plus a starch filler, all mixed together. It works in two stages: some bubbles form when wet, more form when heat hits the oven.

If your recipe calls for baking soda, the acid is already in the ingredient list doing a job. If you swap in baking powder, you are adding extra acid that was not planned for, which changes the flavor and texture. If your recipe calls for baking powder and you use baking soda, you lose the acid needed to set up it, and the cookies do not rise.

Key Takeaways

  • Baking soda needs an acid in the dough to work; baking powder contains its own acid and works without one.
  • Using baking powder instead of baking soda adds unwanted acid and creates a soapy or metallic taste.
  • Using baking soda instead of baking powder leaves cookies dense and flat because the soda has nothing to react with.
  • If you must substitute, you need to adjust the recipe by adding or removing acid and changing the amount of leavening agent used.

When baking soda is in the recipe and you want to use baking powder

This substitution is possible but requires math. For every teaspoon of baking soda called for, use three teaspoons (one tablespoon) of baking powder instead. This accounts for the fact that baking powder is weaker — it is mostly starch, not pure leavening.

However, you also need to remove or reduce the acid in the recipe. If the recipe calls for buttermilk, sour cream, lemon juice, vinegar, or molasses, you will need to replace some of it with regular milk or water. The exact amount depends on how much acid was in the original recipe, which is why this substitution often produces unpredictable results. Your best option is to find a recipe that already calls for baking powder instead.

When baking powder is in the recipe and you want to use baking soda

This substitution is harder and usually not worth attempting. Baking soda is much stronger than baking powder — one teaspoon of baking soda is roughly equal to three teaspoons of baking powder. If you use one teaspoon of baking soda where the recipe calls for three teaspoons of baking powder, you will not have enough leavening, and your cookies will be dense.

You would also need to add an acid to the dough that was not in the original recipe. The recipe was designed without that acid, so adding it changes the flavor balance. Unless you have experience adjusting recipes, this substitution usually fails. Again, finding a recipe that already calls for baking soda is simpler and more reliable.

How to tell which one your recipe actually needs

Read the ingredient list. If you see buttermilk, sour cream, brown sugar, molasses, lemon juice, vinegar, cocoa powder, or honey, the recipe almost certainly calls for baking soda. These are all acids that set up it. If the recipe lists only regular milk, water, or oil with no acidic ingredients, it probably calls for baking powder.

The recipe instructions also give clues. If it says "mix the baking soda with the dry ingredients" or "dissolve the baking soda in the buttermilk," baking soda is the intended ingredient. If it just says "add baking powder to the dry ingredients," that is what you need. When in doubt, check the ingredient list at the top of the recipe — it will say which one.

What happens if you use the wrong one anyway

If you use baking powder instead of baking soda, your cookies will taste off. Baking powder contains cream of tartar, which has a slightly metallic or soapy flavor that becomes noticeable when you use too much. Your cookies may also spread more than expected because the leavening happens in two stages instead of one, and they might not brown as evenly. The texture is usually still acceptable, but the taste is the real problem.

If you use baking soda instead of baking powder, the results are more obvious. Your cookies will be noticeably denser and flatter than they should be. They may also have a slightly bitter taste because the baking soda did not fully set up — there was no acid to react with it. The cookies are still edible, but they will not have the rise and texture the recipe intended.

The easiest solution: use the ingredient the recipe calls for

Both baking soda and baking powder are inexpensive and shelf-stable. If you have a recipe that calls for one and you only have the other, the simplest fix is to pick up the correct ingredient from the grocery store. A box of baking soda costs under a dollar and lasts for months. A can of baking powder costs about the same.

If you are in the middle of baking and cannot get to a store, your best option is to find a different cookie recipe that uses what you already have on hand. Many cookie recipes exist for both baking soda and baking powder, so you have options. Substituting and adjusting is possible, but it requires understanding the chemistry and being willing to experiment — and even then, the results are not may provide to match the original recipe.

Frequently Asked Questions

Can I use half baking soda and half baking powder to make a substitution work?

Not reliably. Mixing them does not solve the underlying problem: if the recipe was designed for baking soda, the acid is already in the dough, and adding baking powder adds extra acid you did not plan for. If the recipe was designed for baking powder, mixing in baking soda does not give you the acid needed to set up it. You would still need to adjust the other ingredients.

What if I use baking soda in a recipe that calls for baking powder but add vinegar or lemon juice to set up it?

This can work, but the flavor will change. You would need to reduce the liquid in the recipe to account for the vinegar or lemon juice, and the cookies may taste sour or tangy depending on how much acid you add. It is a workaround, not a true substitution, and the results depend on how much acid the recipe can tolerate.

Does it matter if I use aluminum-free baking powder instead of regular baking powder?

Not for substitution purposes. Aluminum-free baking powder works the same way as regular baking powder — it still contains acid and starch. The difference is that aluminum-free versions do not contain aluminum compounds, which some people prefer to avoid. For cookie recipes, either type will behave the same way.

How long do baking soda and baking powder stay fresh?

Baking soda lasts indefinitely if kept dry and sealed. Baking powder typically lasts one to two years because the acid and baking soda can react slowly over time, especially in humid conditions. You can test baking powder by mixing a teaspoon with hot water — if it fizzes vigorously, it is still active. If it barely fizzes, it is time to replace it.