I would use two and a half, but since that's not possible, I would get two and have extra batter. Mind you, no matter what batter, a cake/brownie must be 3/4 of the way full. hope this helped:)
4 boxes for a single pan
Most cake mixes are for a 9x13 pan which is 117 sq. inches. 12x12 is 144 sq. inches. 1 mix would be enough and shorten the cooking time by 5 to 8 minutes.
about 1 and a half
for an 14 in round cake pan, you only need 1 box
If you are using a 2" deep cake pan you would need 13.5 cups of batter.
4 boxes for a single pan
Most cake mixes are for a 9x13 pan which is 117 sq. inches. 12x12 is 144 sq. inches. 1 mix would be enough and shorten the cooking time by 5 to 8 minutes.
about 1 and a half
for an 14 in round cake pan, you only need 1 box
There are 11 cups of batter in an 11x15 pan for a 2 inch layer. I would guess for an 11x13, maybe 10 cups?
Twelve Inch Mixes was created in 1992.
144 1-inch squares. 36 2-inch squares.
You can actually use one box alone but it will be thinner. you can actually use the amount of boxes of cake mix you want it will just get thicker.
The Twelve Inch Mixes was created on 1986-06-30.
Ultrahouse The Twelve Inch Mixes was created in 1991.
Okay so here you go! There are approximately 4-5 cups of batter in one cake mix. For a half of a sheet cake, I use 3 cake mixes, so for a full, that's 6. You will have a little bit left over too.
An 8 inch square cake can reasonably be divided into 4 pieces, each of which will be 4 inches square.