So I'm pretty new to doing weddings.... I've done tons of party cakes using the Wilton serving chart (http://www.wilton.com/cakes/making-cakes/baking-serving-guide.cfm) but I'm nervous about trusting the larger numbers for wedding cake sizes.  In your exerience, do catering staff actually get these bigger numbers of servings per tier?? or do you more experienced bakers always give slightly bigger tiers in case the staff cut the pieces too big to avoid a cake shortage?  Thanks!!!

Always leave a cutting chart for the catering staff and be sure to talk to the person in charge about how the cake is to be cut.  I was asked to do a cake and drive it four hours to Chicago because the cost of cake in the Chicagoland area was astronomical.  Not only did I have a three tiered cake but 5 sheet cakes to boot.  The grooms mother had to go to the kitchen and tell the staff to cut the cake pieces larger because the staff was so used to cutting cake smaller.  Because cake is so expensive, they don't cut very big pieces.  Every staff is different and every geographic location has a standard.  I learned a great deal from this experience about the importance of a cake cutting chart and communication with the catering staff.

Don't forget...if you "sell" based on party servings and the caterer cuts by "wedding" servings, an unhappy bridal family will be complaining that you sold them too much cake when they have it left over. And rather than getting bonus points for providing bigger servings, you will get slammed for "over selling" the amount of cake needed.

Stick to industry standards and provide a cutting chart to EVERYONE. The caterer, the planner, the MOB....

Thanks!!!!!!  @johnson, I hadn't ever considered people might be angry with too much cake, but the reasoning makes TOTAL sense, thanks!

second part of this.... I know with wedding cupcakes you're "supposed to" recommend 1.25 to 1.5 cupcakes per guest based on serving method of the cupcakes since people tend to take more than one.  Does the same rule apply to actual wedding cake?    For example, if a bride has 275 guests do you plan on giving a cake and cutting chart for 290ish to give a little extra for anyone who grabs seconds or do you stick to 275 exactly?

Never heard MORE cupcakes than 1 per person. Minis, or multiple flavor choices maybe... but one serving is one serving. No one says the wedding is an "all you can eat buffet". 

I think most recommend less cake than 1 serving per guest, based on a full dinner being served, alcohol, guests leaving early, etc. 

From the famous IndyDebi here on CC:

Here's how I came up with that number. Way back in the day, when I first started and did cakes only, I would stay and cut the cake. I began noticing how many plates I used at a reception and soon began noticing the ratio. After a few months, I noticed, for example, that I never cut more than 125 pcs for a cake that had been ordered for 200. I began really watching and it seemed to be the rule each and every time. That's how I developed my 60% Rule.

Take the total number of people invited (not the number EXPECTED, but total INVITED) times 60%. 3 exceptions: (1) if bride/groom is active military (2) if bride/groom is very active in their church (3) if bride/groom is African-American. Then I suggest that the couple use a 70 or 75% ratio. the one thing I cannot factor is how their family reacts to weddings. I also ask if there are any special events around the wedding (i.e. Had one wedding that took place on family reunion weekend. Everyone flew in a day early for the Friday wedding. She ordered cake for 150 and we served 165. Didn't run out of cake, either!)

So when you ask Why would it be just 60%? Is it that not everybody eats cake?, it's not 60% of those in attendance .... it's 60% of the total number invited. I don't know of anyone who has a 100% show-rate at their wedding.

This information becomes a great sales tool for me because I can help brides stay in budget. When they are not spending money on people who wont' be there anyway, then they find they CAN afford that chocolate fountain or that other extra they thought they couldn't afford. (And then they think I"m great!
Read more at http://www.cakecentral.com/forum/t/365913/wedding-cake-servings-rule-of-thumb#RYJ2g3bP3u6Jzd9J.99