Hi,

I've been looking at the Wilton chart and the  7" round servings section is blank.  I'm making a cake for around 20 people and I was thinking of making a 2-tier cake, bottom would be 7" and top would be 4".

That should be good for 20, right?

http://cakedecorating.about.com/od/planningstage/a/Cake-Sizes-And-Portion-Sizes.htm

According to this chart a 7" round cake feeds 15, a square feeds 24

AWell, if a 6" serves 12 and an 8" serves 24, then I'm gonna go with a 7" serves 18. Keep in mind that those pieces are small (I don't use wilton's chart) so if the cake is the only desert, you may need more.

7" round = 19

7" square = 24.50

http://shinymetalobjects.net/cake/calculator/cakulator.html
 

AAlso remember that all the serving charts in the world won't help unless the cake gets cut according to the chart. Basically, the cake feeds however many the person cutting it says it feeds.

True!  I will give them specific directions.  Maybe I should do an 8" and a 5"?

AThe first wedding cake I ever did was for my brother-in-law. They had a very small wedding (25-30 people) but the bride had her heart set on a 3 tiered cake. The cake was our (I'm including my husband but really it was all me;) ) gift to them so I did what she wanted. It was designed to feed 53 using Earlene's chart(74 servings using wiltons chart). I sat back and watched that cake get demolished by less than 30 people!

Moral of the story: if your cake is really tasty, plan for more instead of just enough!

Unless, of course, you're selling the cake. Then you would need to go over the serving sizes with your client and let them decide. I didn't get the feeling that you're selling it though...