You will want to use a standard baker's half-sheet pan, which is 13x18 inches. It's probably the most common size baking and the one most of us have 2 or 3 or 8 of floating around in our kitchens that we use for baking cookies or making sheet pan dinners. If for some reason you don’t have a half-sheet pan handy, you can also use different sized baking pans to make this sheet cake. A 10x15 inch jelly roll pan or a 9x13 baking dish will both work, but keep in mind that you will need to adjust the baking times since both pans are smaller and will take longer for the cake to bake through.