Cake Baking - Portage,MI

It would be a very thin cake - if that's what you want, check to see if it's done as early as 10 or 15 minutes. If you don't want a paper thin cake, use at least two boxes of mix. A standard box of cake mix yields about 5 cups of batter. A jelly roll pan that is 1" high would take 10 - 15 cups of batter to fill depending on how high you want the layer and how deep your pan is. I typically use two boxes of mix (with usually a small amount of batter left over) for a 13x9x2 pan and that actually bakes to 2 inches high, filling the pan up.

Standard boxed cake mixes are usually made for the following pan sizes and times:
2 - 9" pans or 1 - 9" x 13" pan or 24 muffin cups filled 2/3 full.
Bake for the following times: 9" pans, 22-26 mins; 9x13, 25-28 mins; muffins 18-22 mins

You COULD bake it in that 11x15' pan, probably for about 25 minutes, but you risk having a very thin cake. Be sure to grease and flour or you'll have quite a time getting it out. Also, free the edges and put it in the freezer for 30-45 minutes once it's cooled...this will make icing it RIDICULOUSLY easy.

It would be very thin. But two cake mixes are about perfect if you bake it for 35 (sometimes 40) minutes.

try going on www.allrecipes.com and search cake pan size conversions. this may help answer your question. hope this helps.

if the sides are deep enough, you can make a wall of foil to shorten the pan. Otherwise, it will be a thin layer of cake. Which might work fine, cuz you could cut it in half and stack the layers, with icing in the middle.

JB read my mind and beat me to the answer : )