Homemade baking powder can be mixed from three common pantry ingredients: one part baking soda, one part cornstarch, and two parts cream of tartar. The source notes that some people say the homemade version has fewer metallic undertones than commercial baking powder.
For a single teaspoon of homemade baking powder, the source provides this equation: 1/4 teaspoon baking soda + 1/2 teaspoon cream of tartar + 1/4 teaspoon cornstarch = 1 teaspoon homemade baking powder. That equation was added in a September 2, 2010, update to clarify the ratio.
The formula relies on the same acid-base reaction that commercial baking powders use. Cream of tartar, an acidic powder, reacts with baking soda, a base, to produce carbon dioxide. Cornstarch acts as a filler and helps absorb moisture, which can otherwise cause premature clumping or reaction.
No additional ingredients, equipment, or storage instructions are provided in the source material. The claim about metallic undertones is attributed to unnamed individuals and is not supported by a cited test or manufacturer statement.
Editorial Notes