I made a 9 in cake, 4in high. I only got 18 slices out of it, is that about right or should I have gotten more?

..moving to Cake Decorating.

Yes... a 9" cake should easily get 25-30 standard (1x2x4") slices. Wilton's wedding chart says 32 and the party chart says 24 I believe. You wouldn't cut it into wedges though... you'd have to cut it like a wedding cake.

http://www.cateritsimple.com/id10.html this is a great visual on how to cut a cake and get the proper servings. hth's!

round or square?

It is round, but I guess I have been cutting it wrong, because I cut it into wedges.
If it were a 8in square how many would I get?

an 8" square is 30 wedding servings.

How about an 8in square party cake?

Here's a link to all four of Wilton's cake preparation and servings charts for all pan sizes by shape:
(See: baking time and batter amounts.)

http://www.wilton.com/cakes/making-cakes/

HTH

I use this chart because I think it is closer to the realistic serving sizes. http://www.baking911.com/cakes/numberofservings_guide.htm

Mug-a-Bug, that link isn't working. But if you post a link to Earlene's cake serving charts (source for the above link) that will work.

I find that Earlene's is way too big for weddings, but alot of people use her chart. Just make sureyou charge enough per serving to cover the cake. Bigger servings warrant bigger prices. According to Wilton an 8" square is 20 party servings.

The wilton 8" square will yield 32 servings cut at 1x2x4 (8 cubic inches of cake) to me a party size is 2x2x2 which is also 8 cubic inches of cake so no difference in size or amount of cake served.