Found this on another forum

"Baking soda is sodium bicarbonate - a base. Baking powder is a mixture of sodium bicarbonate and a weak acid such as monocalcium phosphate, sodium aluminum sulfate or tartaric acid. When you dissolve the baking powder in a liquid, the acid and base act together to create gas. This is called chemical leavening - making baked goods rise without yeast.

If you substitute baking soda for baking powder, you’re missing your acid, and your cake or bread will not rise, or at least will not rise as much as expected.

If you don’t have baking power, you can add extra acid to your batter in the form of buttermilk, vinegar or cream of tartar. You can substitute 1/2 tsp cream of tartar + 1/4 tsp baking soda per teaspoon of baking powder called for in your recipe."

https://www.healthline.com/nutrition...OC_TITLE_HDR_2

"Baking powder may be used as a replacement for baking soda. Remember that baking soda has 4 times the power of backing powder, so 1/4 teaspoon baking soda is equivalent to 1 teaspoon of baking powder. For example, if a recipe calls for 1 teaspoon of baking soda, use 4 teaspoons of baking powder as a replacement."