It is possible to use baking powder as a substitute for baking soda. For a straight substitution, use three times as much baking powder as baking soda. For instance, if a recipe calls for 1 teaspoon of baking soda, add 3 teaspoons of baking powder instead.
Less baking powder is needed if the salt in a recipe is omitted. This method calls for a two-to-one substitution. Therefore, if a recipe calls for 1 teaspoon of baking soda, leave out the salt and baking soda and add 2 teaspoons of baking powder instead. Substituting baking powder for baking soda does change the flavor of the dish.