How much cream of tartar per egg white?

Typically, you can use about 1/8 teaspoon of cream of tartar per egg white. This helps stabilize the egg whites while whipping them, making it easier to achieve stiff peaks. For example, if you are using three egg whites, you would add about 3/8 teaspoon of cream of tartar. Adjusting the amount slightly is fine, depending on your recipe and desired texture.