I'm hoping someone can help me with this. Although I've found several charts used to determine the amount of fondant needed to cover a cake; it isn't really help me b/c they're all usually based on cakes that are 4" high.

I'm trying to determine the amount of fondant needed to cover a jukebox cake, realizing that I won't be covering the cake in one piece. The bottom section of my cake's dimensions are 12 x 8 x 12 (height). I'm anticipating having to wrap the fondant around the cake like a book; but I'm trying to figure out how much fondant in inches I'll need to roll out and; how does that convert to pounds of fondant that will be needed??

What is the math being used??? When I showed my husband Toba Garrett's book that gave a formula in which for an 8 x 3 inch cake; her instruction was to multiply 2 x 3 (cake sides) + 8 + 2-4" additional. Based on his understanding of figuring out area; he didn't understand why only 2 sides were being accounted for? This example may have been for a square cake. What then accounts for the other 2 sides that should be accounted for?

Thanks