I have a wonderful recipe that works with 2 of the 9in. round cake pans. How do I know what size sheet cake pan to use for this same recipe?
do you know how many cups of batter you get from the recipe?
I'm thinking it would probably fill an 11"x15" cake
Each pan takes a different amount of batter. You need to know how much batter a recipe makes so you know how much to make for your pans.
Most recipes that can be baked in 2 8 or 9 inch round pans will work with a 9x13 pan.