I have someone who will build me cupcake stands, but i need to figure out dimensions of the actual stand to fit 17-18 dz cupcakes all together.  The top tier will have a 6" cake on top (so a 8" round top tier), so i won't be able to fit any cupcakes on top, so that leaves me with 4 tiers to fit around 216 cupcakes.  What are the next 4 tier sizes i would need?  is there a website that has this information? also, they will be round.  Thanks everyone for you help!

Is there a website? No there's high school math.

First of all 18 dozen cupcakes is 216

You want to give the finished decorated cupcakes a finger's worth of space if possible, to allow them to be served.  If you are asking about standard 2.25" cupcakes, this would be 3" give or take.

So these cupcakes are going to sit in rings that are 3" deep==1.5" on each side of the centre line of  imaginary circles on your stands.

So you use the formula for the circumference of a circle (C = 3.14 x diameter) to calculate how many cupcakes you can fit into a circle.  Remember that on a 14" plate you are using the circumference of 12.5" NOT 14".

So here you go--do the calculations for various sizes of plates (assuming that you will have one ring of cupcakes per plate).  You can also figure how many cupcakes would go into a second ring on some of the larger plates.

Then add up enough cupcake places to get 216.

You might find that a 6" cake will look a little small, maybe you will have to suggest an 8" top cake.

Even is all the cupcakes don't fit on the stand, you can surround the stand (especially if it has little feet) with more cupcakes on the tabletop.  I do that all the time and it looks fine.  And I always use a 6" on the top - IMO it's the perfect size.  I'd talk a customer into a 6" from an 8".

math was never my forte, so thanks for the equation.  My husband on the other hand is a math wiz, so I'll give this to him and let him figure it out =)