AI will be doing my very first wedding cake in May and the bride to be requested 6" tiers for a 3 tier cake. All of the charts I have found are for 4" tiers. I assume the slices will be smaller with an exra layer of cake so I'm not sure what to go by. Has anyone dealt with this? Also, I read somewhere that you don't count the top tier in the number of servings. Is that standard? I asked if she wanted a tier for her and the groom to save but she didn't really give me an answer. Last question (for now), would you asseble the cake at the location? Or deliver it assembled? Thanks so much for your help!

There are pans that are 3 inches deep which will give the 6 inch high tiers.  But also when using the 2 inch deep pans, keep in mind that by the time you add the filling or icing between the layers, that will add additional height to each tier as well.  Torting the layers can also add height as well.  If the cake is stacked and if you have never stacked a cake before, I would recommend to not assemble until you got to the venue.  Often you can safely stack the bottom and middle tier for transporting but I would definitely stack the top tier on site. Typically the top tier is not counted towards servings.  There is a chart on Wilton's website that can give you an idea of serving sizes.  This one is for 3 inch deep pans.http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-3-inch-pans.cfm

  Also there is information for how to stack a cake there as well 

http://www.wilton.com/cakes/tiered-cakes/stacked-tiered-cake-construction.cfm

yes everything they said. heheh! seriously, i would also recommend you to assemble on site. also, check out videos on how to stack cakes but basically it is important to support it with dowel rods and, when you choose to deliver a cake already assembled, a main dowel rod must be pushed all through the three tiers for stability.

Also, warn the reception site that the tiers are going to be taller than normal. They don't always fit on the dessert plates really well if they're 6" tall, and the venues that I know HATE cutting the taller cakes because of it.

I do 6" tiers as 2 cakes, with a cardboard and supports in between. But, it is actually about 6 and a half- 7" after I am done! I use 3 layers of cake in each part, building from the bottom up, cardboard, cake, filling, cake, filling, cake, icing on top, supports, wax paper, cardboard, REPEAT, skewer together,  Then ice and fondant as usual.

For the serving count, I use 75% of what the Wilton chart shows a 4" serves, and multiply by 2. So, an 8" wide cake, 6" tall is 32 servings. of, course, there are MULTIPLE ways of figuring it and getting the same answer, but I am dyslexic and can confuse myself easily, and this works for me.