The bride I'm working with wants 2 cakes that have the same number and sizes of round tiers, and she is saving the top of both. She has 250 people at least attending her wedding which is in 2 weeks. I came up with 6" (not being served), 8", 10", 12" for a total of 118 servings per cake or 6" (not being served), 8", 10", 12", and 14" for a total of 196 per cake.  Are there any other options? She is fine with the almost 400 servings, but that is going to be massive amounts of cake.  I've done plenty of wedding cakes, but I think it's the amount that has me going bonkers. Would appreciate any help! 

4 x 6 x 8 x 10 x 12 then all five tiers serve about 140 -- remove the 4" and the servings are 135  so double that and you've got 270 -- be sure to charge for all that -- just 'cause she's not serving it it's not free right?

also you can plug in any combinations you want on this website:

http://capitalconfectioners.com/cakulator/cakulator.html

Seldom can we come *exactly* to the # of servings needed.  Give the bride a choice which she wants - over or near the magic #.  And as K8 said, charge for the # you make - especially if it's over.   Another thing to consider is about 10% of those invited will not show up  - some even though they have responded that they would be there.

Thanks for the help- it is greatly appreciated : )