Hi! I made you guys a present! This convenient chart gives the volumes for a variety of baking pans. That means, if you have a recipe that calls for a 10- by 10-inch baking pan, you can see that you could also make a two-layer cake out of the same amount of batter in two 8- by 2-inch round baking pans.
Of course, cooking time will have to be adjusted based on how thick your pans are, but always err on the side of too little time, and you should be fine!
(Click the image below for a printable PDF!)