Wilton chart says 23, but I find this hard to believe. I would imagine it would be closer to 40 if you are cutting 1.5" w by 4" h. Anybody know for sure?

I'm not sure which chart you're looking at, but a 9x13x4 inch cake serves 50 (1x2x4"):

http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-2-inch-pans.cfm

Even the party servings are listed at 45 (1-1/2x2x4):

http://www.wilton.com/cakes/making-cakes/baking-party-cake-2-inch-pans.cfm

HTH

9x13 two layers should feed 45 according to Wilton-But 40-45 is definitely the correct amount. I think 23 is probably for one layer

http://www.wilton.com/cakes/making-cakes/baking-party-cake-2-inch-pans.cfm

Thanks guy....I don't trust Wilton for anything. It is a chart in the back of a yearbook I have that says a 2 layer party cake 9x13 has 23 pieces.

I see that my chart is exactly the same as the one they have posted online except they have revised the serving amounts for ALL the cakes.

My chart says a 2 layer 6" cake has only 8 pieces and I see the new one says 12. Glad they realized it was wrong. Guess I need to throw my old chart out!

The number of servings depends on how big each serving is.

A 9x13 cake is 117 inches, squared in surface area.

If your servings are 1x2 inches, then each serving is 2 inches, squared in surface area.
117 / 2 = 58.5 So a 9x13 yields, 58 1x2 servings.

If your servings are 1.5x2, then each serving is 3 inches, squared in surface area.
117 / 3 = 39 So a 9x13 yields 39 1.5x2 servings.

If your servings are 2x2, then each serving is 4 inches, squared in surface area.
117 / 4 = 29.25 So a 9x13 yields 29 2x2 servings.

Standard size of a single layer (2" tall) cake serving is 2x2x2.

Single layer 9x13, when cut in approx 2x2 squares means the cake will be cut in 4 rows by 6 columns = 24 pcs.

Standard size of a double layer (4" tall) cake serving is 1x2x4.

Double layer 9x13, when cut in 1x2x4 pcs means the cake will be cut in approx 8 rows by 6 columns = 48 pcs.

I always round down to the nearest even number as this allows for any cake shrinkage and, if you tried to cut in EXACTLY 2" rows, you'd have an odd sliver left over on the end.

That's why I round down ... to keep it simple ... and that's why I use the words "approximately".

i am agreeing with janh... the WILTON CHART.. that i am looking at.. says 50... NOT 23.. i have always known that a 9x13x2 feeds UP TO 24.. so if you double it.. it will feed 48-50... so WILTON hasn,t led us astray. right?

I love your "tude" about this!  Just saw one post that claimed 96 slices in a 9 x 13 x 4-- giving a whole new spin on "give me a small slice of cake."  But seriously, with this size pan, you can't cut it in 1 x 2 inch pieces-- more like 1.5 x 1.75 to get the pieces even, and that will only give you 40 pieces.  I'm not pointing this out to be nit-picky, I just wish they would standardize these charts and get real-- what's the point of a piece of cake so small it falls apart when you slice it, or so tall it won't fit on a plate?