How many cups does 1 box of cake mix contain?
According to LadyCakes' website, a boxed cake mix yields 4 to 5 1/2 cups of batter. Hope that helps.
It usually has a yield on the package somewhere. Just bear in mind that if you are using add in's or buttermilk, etc., it could change.
Duncan Hines gives 5 cups. But when I add more milk or add sourcream or buttermilk it goes further...