My church is celebrating its 40th anniversary this year, and I get to make a cake to feed 800-900 people! My plan is to do ten, two-layer 16-inch  squares in a two cakes by five cakes configuration and frost them all as one giant cake -- 32" x 80" x 4".  Assuming no torting (just one layer of filling between two 2-inch layers), how can I figure out how much buttercream I'll need? It won't be just 10 times the regular 16" x 16" cake amount, since not all the sides will be covered, and that's quite a bit of difference in area.

Thanks!

~Valerie

One 16" by 16" square cake that is 4 " tall, including one layer of frosting as filling:

top is 256 sq inches

filling surface is 256 sq inches

sides are 4 x 16" x 4" = 256 sq inches

total surface area to be covered is 768 square inches

The big cake is

2560 sq inches for the tops

2560 sq inches filling surface

sides are 64 x 4"  plus 160 x 4"  = 896 square inches

total surface area to be covered is  6016 square inches

6016 divided by 768 is 7.833

you will need 8 times as much as you would need for a single 16" square frosted on all sides.  (I don't know how much that would be - depends on how thickly you apply the frosting!)

Wilton charts are pretty generous but following yortmas'  calculations - 11 cups per 16" square × 8=80 cups of icing

Thank you both SO MUCH! I finally made it to the store today to price ingredients, and now I have enough info to apply my own math skills and figure out what this thing's gonna cost. ;^)

~Valerie