I am making a topsy turvy cake for a wedding. I'm really having trouble figuring out the serving size. They are expecting about 250 guests, but will also have cupcakes, so they don't care if the cake has enough servings for everyone, plus not everyone will want cake, so I'm thinking 150-200 servings. It will have four layers. Each layer will have 3 x 2" layers of cake/filling. So in total I will have 12 x 2" layers. I was thinking of doing 3 x 6", 3 x 8", 3 x 10", and 3 x 12" layers, but would that be enough?
Also, how on earth do I figure out how much filling and fondant I will need? I don't want to underquote but I'm totally an amateur decorator and have no idea how to figure out how much fondant I will need.
Based off of the standard wedding serving size http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-2-inch-pans.cfm a 6-8-10-12 cake will serve 130 guests. Adding another layer on each cake will add about 40-50 more servings uncarved but depending on how you construct/carve the cake, you may eliminate half of those servings. i.e. if you taper the bottom of each tier and cut half of the third layer of cake off.
What I do to offset this is to charge my base price plus $1 and use the servings of the middle layer in each tier. For example, if one of my tiers has an 8" on top, a 7" inch in the middle, and a 6" on bottom (useful when tapering the tier to get the look I want), I price the base price plus + a dollar times the servings a 7" regular tier would yield. Yes, the customer is getting taller slices but you're making up for the loss of cake you're carving and the time spent carving it by adding the extra dollar. Keep in mind that the customer will most likely cut the cake the same way so the serving amount sizes would be the same except for the height.
Another way I've seen it priced is by cubic inches. That way you're charging by amount of cake versus amount of servings. Another way to price is to charge for the amount of cake and let the customer know an estimate of how many servings you'll be cutting off. That way the customer pays for the cake you use and the cake that goes to waste after carving as well. They might think they're wasting money by paying for unused cake but you still have to bake that amount of cake and you're taking extra time to carve the tiers. Hope that makes sense.
Filling amount should be 1.5 the amount you use for a regular 2 layer tier of that size to account for the extra layer. The link posted above also has that info. As far fondant goes, here's a site to help with that: http://www.wilton.com/decorating/fondant/fondant-amounts-to-cover-cakes.cfm . Since you're tiers will be 6-7 tall, I would multiply these amounts by 1.5 also.
Hope this helps!