I'm doing a 3 tiered cake that needs to serve 100. The top tier is going to be a half ball that I will carve myself. I'm not sure how serving to count that top tier. Which would be the best sizing combination for this type of cake.
Please help!!!

I guess it all depends what shape the second and third tier cakes are going to be. Also, I believe a regular 6 inch cake will serve around 10-12 people so if you are carving away at this then it would serve less. Hope that makes sense.

Ana

Wilton's chart:
http://www.wilton.com/wedding/wedding-cakes/wedding-cake-data.cfm

Earlene's chart:
http://www.earlenescakes.com/ckserchart.htm

For what you are describing, I would probably use a 14" and 10" round as my bottom 2 tiers.