I am making two 9x13 cakes. How many cups of batter do I need for each pan?
My matrix says 6 cups for a single layer 9 x 13. HTH
I find one of the easiest things to do when you need to know how many cups of batter you will need for a particular size pan is to use water to measure first. Just pour the water in, count how many cups you needed to fill to the desired amount and voila you have the amount of cake batter you will need.
Oh, and welcome to CC!