I am making a tiered cake for a party. It will be served after a full dinner and guests will also be drinking alcohol. The original projected head count was 150 people. I was planning on doing a 3 tier, 14, 12, 10 inch cake which I thought would be more than enough. I was just informed the head count has now gone up to 200. Will my current plan provide enough servings?
According to the Wilton serving chart for party size pieces, 2" x 2", your three tiers will make 90 servings. If you want to stay with the same size cake, you should make sheet cakes to fill in the balance. It is very unlikely that 200 pieces will be served, but if I am doing an order for a paying customer, I am going to give them enough cake to serve 200, if that is what was ordered. Don't forget to charge accordingly!
Your current set-up will provide 172 servings. You could add an 8" to the top which will bring you up to 196 servings.
I know that not everyone will eat dessert but I am not a fan of not having enough for every person because you just never know. Maybe everyone will have a slice? Also, if the venue plans to plate and serve slices of cake to everyone then you definitely need to have enough servings for pretty much every person.
I like to use this chart (https://www.wilton.com/cake-serving-guide/cms-baking-serving-guide.html
Oh and FYI, I used the wedding serving chart, not the party. I tend to use the party for smaller gatherings when catering staff won't be there to cut the cake since normal folks tend to cut larger pieces.
Let yor client decide if they want to go with a bigger cake. From what you said...full meal, drinking etc you can expect fewer people to want dessert. Personally I would stay with the original sizes but as Freckles said just adding an 8"er will bring it up just right.
Also at many events about 10% of those invited don't show and/or don't want sweets.
Thanks for the advice everyone. This cake is actually one I am donating to my 50 year high school reunion party, so how much to charge is not an issue. I just want to make sure I have enough. Venue staff will be serving the cake.