Baking powder is a precise leavening agent. Here's exactly how to replace it without throwing off your recipe.
Baking powder is a chemical leavening agent — a pre-mixed combination of baking soda (sodium bicarbonate), an acidic component (usually cream of tartar or sodium aluminium sulfate), and a starch (usually cornstarch, which absorbs moisture and prevents premature reaction).
Most commercial baking powder is "double-acting" — it reacts twice: first when it contacts moisture (producing initial bubbles that begin to lift the batter), and again when heated in the oven (producing a second burst of gas). This double action provides a forgiving window between mixing and baking.
Understanding what baking powder is made of is the key to substituting it — you are simply recreating the acid-base reaction using other sources of acid and base.
FUNCTION: Chemical leavening via acid-base reaction producing CO₂
Cream of tartar (potassium bitartrate) is a dry acid. Combined with baking soda, it recreates the precise acid-base reaction of baking powder. This is the most chemically accurate substitute.
The acid in lemon juice reacts with baking soda to produce CO₂. Note that lemon juice is a liquid — it adds moisture to the recipe. Reduce other liquids slightly to compensate.
Identical function to lemon juice. White vinegar is more neutral in flavour.
If your recipe includes buttermilk (or yogurt, or sour cream), you already have an acid source. Reduce or eliminate the baking powder and activate with the acid already present.
Self-rising flour contains AP flour, baking powder, and salt in a fixed ratio (1 cup AP flour + 1.5 tsp baking powder + 0.25 tsp salt). Swap self-rising flour for the total flour in the recipe and omit added baking powder and salt.
Beaten egg whites provide lift through mechanical air incorporation rather than chemical reaction. Add whipped egg whites by folding gently into the final batter. This works best in recipes with enough structure to hold the air (cakes, soufflés) rather than dense cookies or quick breads.