Sorry, I edited this post already!  You are all so kind to respond so quickly.  : )

I have been asked to make a sheet cake for a St. Patrick’s dinner.  I plan to make an 11x17 cake, 2 layers.  Up to how many will this serve?  I must be blind, because if there is a reference to this in either the Cake Bible or Heavenly Cakes, I cannot find it.  Thanks!

I always just try to visualize how big I want one slice to be, and figure it out from there. For example, if you wanted small 2 x2 slices, then you could get 108 portions—12 across and 9 down, 12x9=108

...3x3 would be 48 and so on…

Matthew, thanks, I think I get the math now.  11x17, 2x2 inch pieces - 8.5 x 5.5 = 46.75 servings. My math skills are not good, LOL.

Yes, that’s right, will that be big enough slices?  Before you updated, I was thinking that first cake was going to be really big!

My brain wasn’t in gear, LOL.  It will have to be big enough slices. I think there will be more desserts there as well.  Or I shall have to make two cakes, yikes.  I don’t know how many people will be coming yet.

Yes, will help for planning when you know the final number. Also wanted to point out that in reality, you’ll probably only get 40 servings: 5 slices down the 11’’ side and 8 across the 17’’ unless you get really particular about the 2 inch slices, then you would have some 1x2 slices leftover (just because 11 x 17 isn’t evenly divided by 2).

Thanks, appreciate your help.  : )