Many people think baking powder and baking soda are interchangeable, but they’re absolutely not! Although they both help batters and doughs rise, they have different chemical makeups. Baking powder has baking soda in it, but it has additional ingredients that make it react differently when mixed into batters or doughs.
Baking soda is a base that when mixed with acids bubbles. Baking powder is made of baking soda and a dry acid. It reacts differently depending on what is in your batter or dough.
It is possible to substitute one for the other. Substitute 2 or 3 tsp of baking powder for 1 tsp baking soda. Substitute 1/2 tsp of baking soda for 1 tsp baking powder and 1 tsp vinegar or lemon juice.
How long do they last? Baking powder has a shelf life of 3-12 months. If you live in a humid climate, it expires more quickly. To test your baking powder, put a small amount in a bowl and add water. If it bubbles it’s still good. Baking soda lasts much longer as long as it’s sealed and kept cool. It doesn’t have an expiration date. To test your baking soda add a bit of vinegar. If it bubbles, it’s still usable.