I wasn't sure what to put this under.

I have mainly a cupcake business  but have begun cakes. I have done 2 tier cakes for birthdays, showers etc.

I have a bride who loves my work and wants an extremely simple buttercream cake for her wedding. She says her guests are not huge dessert people and there will be other items so she wants a cake for 120 servings assuming not everyone will eat cake.

What is your go-to for 120 servings? Is there a great standard tier size that makes this up?

Thanks!

Kirstin

Here you go: Cake Baking and Serving Guide

craftyb gave you a good chart often also used for for party sized cake servings which are a little larger than traditional wedding cake servings -- wedding cake servings sound small but they are a nice size, most adequate and the following chart has been the norm for decades for weddings at 1x2x4 inches -- 

http://www.wilton.com/cms-wedding-cake-data.html

i have always used this chart, which is the industry standard, plus a few extra servings added in unbeknownst to the client to allow for a dropped serving, miscut or if a dowel eats a serving --

so it's just up to you as to determine what size servings you will offer -- 

earlenescakes.com also has a popular chart -- i think it ranges between the other two

http://www.earlenescakes.com/ckserchart.htm

so your job is to determine what size you will sell and to inform your client so they get the proper cuts -- if they want to serve a different sized serving they order more or less cake accordingly -- you stay put once you decide

if you're not already saturated :) there's a cakulator that you can plug in different configurations and it figures it for you

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

best to you

You really should use the wedding cake chart.  Why?  Because that's what every caterer everywhere knows and cuts by.  It you use the party chart or Earlene's chart, and YOU are not there to cut the cake, then there will be lots left over.  You will have charged the bride more for cake her guests will not eat, or you will have given away free cake.  Neither is a good thing.