If you run out of baking powder when you need some, use 2 level teaspoons cream of tartar to one teaspoon baking soda. This is equal to 4 teaspoons of tartrate baking powder, the kind you usually have in the kitchen.
By Evelyn from Greeley, CO
1 teaspoon Baking powder can be replaced with:
1/4 tsp. baking soda plus 5/8 tsp. cream of tartar
1/4 tsp. baking soda plus 1/2 cup buttermilk or sour milk (decrease liquid by 1/2 cup)
1/4 tsp. baking soda plus 1/4 to 1/2 cup molasses
1/4 tsp. baking soda plus 1/2 Tbsp. vinegar or lemon juice used with sweet milk to make 1/2 cup liquid (decrease liquid by 1/2 cup)
Source: University of Illinois Extension