There are many ways to substitute baking powder. Most of the ways you can substitute baking powder is with a combination of baking soda and another ingredient. Baking powder is and important ingredient, so it is always best to use it if you can. There are other substitutes that you can use, healthline has a few more, but I try to give you the ones that I believe are the best.
Cream of Tartar
Baking Powder is made of cream of tartar, baking soda and sometimes cornstarch. Since baking powder contains cream of tartar, this in my opinion is the best replacement. For every 1 teaspoon of baking powder, substitute it with ½ a teaspoon of cream of tartar and ¼ teaspoon of baking soda.
I recommend using cream of tartar as a replacement, but here are a few more.
If you are making a dessert, molasses might be the way to go. You can replace 1 teaspoon of baking powder with ¼ cup of molasses and ¼ teaspoon of baking soda. You may want to cut the amount of liquid ingredients a little bit, so it keeps the right consistency.
Vinegar is a great substitute if you only need a small amount of baking powder. It will leave a sour and bitter taste if you use to much. Substitute the baking powder with ½ a teaspoon of vinegar and ¼ teaspoon of baking soda instead of 1 teaspoon of baking soda.
Similar to the Vinegar, lemon juice may alter the taste of your dish, unless used in a small amount. You can use ½ a teaspoon of lemon juice and ¼ teaspoon of baking to replace 1 teaspoon of baking powder. If you use to much it may make your dish not taste the proper way.
Self Rising Flour
Self Rising Flour can be a great and easy replacement. All you need to do is switch your All Purpose Flour, cake flour or any other flour for self rising flour. Apart from that, you just leave out the baking powder and the baking soda if there is any.