1/2 c butter 

 = 

1 stick or 4 oz

1 t baking powder

 = 

mix 1/2 t of cream of tartar with 1/4 t baking soda

1 t baking soda

 = 

If your recipe has no acidic ingredients, use 4 t baking powder

1 T

 = 

3 t

4 T

 = 

1/4 c