The most common question a baker will ask is: how many cake tiers do I need for X amount of guests? Cake tiers range from 4″ in diameter to 18+” (it must be pretty awesome to have an oven large enough to accommodate 20″ diameter pans!) and are usually 4-5″ in height.
When I was an amateur baker I took a lot of care in measuring my cake pans to calculate the correct servings. Thanks to my engineering background I even used math for my calculations! My equation was simple for a 2″ tall cake:
C=πD (C= circumference, π=3.14, D=diameter)
I add 10 servings for every additional inch in cake height.
It boggled my mind when I started talking to other cake decorators and they were quoting 25 servings out of a cake that I could (and personally have) cut 50 servings from! I didn’t understand how that was possible, math can NOT lie! To add to this confusion, the cake decorators told me about iPhone apps they used to calculate the servings for them and the program was also quoting low numbers. For example, I can serve 18-20 slices from a 6″ tier that’s 4″ in height, but other bakers quote 10-12 servings!
I consulted with a math genius friend of mine, and this was his answer (loved it!):
“For a 6inch cake: So the circumference is roughly 18inches. Doing some trigonometry, with each slice having 3 inch long sides, and a base angle of 20degrees (360/18), each slice will have width (at the widest point) of a little over an inch (1.026 inches to be exact). And the curvature length is 18.84/18=1.0466 like you said.
So in my mind, each slice is roughly a triangle with dimensions 3x3x1.026 inches and a depth of 4inches , and this is understated because it doesn’t include the part that is between the curvature and the 1.026 inch side of the triangle. I think that’s a decent size for a slice.” Apart from being a math genius, he was also raised around a catering business, so I’m pretty confident he knows what he’s talking about.
I have personally called every customer the day after their events to touch base with them and ask how everything worked out. I KNOW my cake calculations are correct because I always ask my customers how the servings worked out for their events. They always say it worked out perfect and half the time they even have some left over!
Take a look at my serving chart, and use this to guide you when ordering a cake. I can’t control how your venue serves your slices, they may cut them way larger than necessary, but these are actual servings you can get from these tier combinations.