Hi all Long time lurker, first time poster.

I'm doing my first wedding cake for a friend this weekend (well everything is baked but the sheet cakes). It a 6, 8, 10 in tiers, then I'm doing a half sheet cake (12x1 to accommodate for the extra guests.

Wilton's guide says...
8 in = 24 servings
10 in = 38 servings
total: 62

So now I need enough cake for 100 people... some guides/forum posts say a 12x18 is enough for 50 people, some say it's enough for 100. Wilton's party guide for the 12x18 says 72 servings, then their wedding guide for 16x16 cake says 128.

I was planning on baking 2 so it would be 4 inches high and I could do my planned orange curd filling in between. Does a 4 inch cake help stretch it to 100? I really just want to make sure there it plenty of cake..

TIA!!

http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-2-inch-pans.cfm

A two layer 12x18 would serve 98 according to the chart above. This is based on 1x2x4 in serving sizes.

do most people find Wilton's serving guides on point? If so, I have exactly enough servings...

It's the industry standard, so long as the person cutting the cake cuts it as advised with Wilton's diagrams and measurements you will have the required number of servings.

Here's a Wilton Cake Calculator

http://shinymetalobjects.net/cake/calculator/cake_calculator.cgi

just punch in pan type and sizes and it gives you numbers for batter, slices, icing, etc...