As you may have gathered, you cannot simply substitute one for the other.
Baking soda is 100% sodium bicarbonate. Sodium bicarbonate is an alkaline salt substance that creates carbon dioxide gas when mixed with acidic ingredients. Acidic ingredients like buttermilk (of buttermilk pancakes fame), vinegar (ala kids’ science fair volcano experiments) or lemon juice.
Baking powder, on the other hand, is a combination of sodium bicarbonate and a dry acid like cream of tartar which requires moisture and heat to activate for it to make bubbles (which is the “double-acting” part of “double-acting baking powder.”)
You can use baking soda or baking powder in a recipe or both together, depending on what the other ingredients are. Baking soda by itself will do absolutely nothing without some kind of acidic ingredient to activate it, no matter how much you add into it. It will just make your recipe taste soapy or salty.
When making substitutions, keep in mind that baking soda is 3-4 times stronger than baking powder, so you'll need a lot more baking powder to get the same leavening action.
You would have to use approximately 3 time the amount of baking powder as backing soda. So, 1 tablespoons of baking soda equals 3 tablespoons of baking powder.
