AOk so I really love the ultimate vanilla cupcake recipe found here. http://www.cupcakeproject.com/2011/09/ultimate-vanilla-cupcake-test-baked-by.html I need to make a 3 (1inch) layer 10" cake. But I really don't know how. Is the a conversion chart of cupcakes to cake?

I'm not sure, but I did weigh a baked cupcake and an 8" 2 layer (4" high) cake a couple weeks ago,and the math worked out to 26 cupcakes to an 8"... hope that makes sense! 

I would go for at least 45 cupcakes worth of batter, for a 10".

AThanks that is very helpful

yay!

AI have to make extra cupcakes too so I guess either vwsu it will work out

When I use that recipe for cupcakes I get 18 regular size cupcakes.

ASo I am gonna try a 2 1/2 or should I just make a 3x?

It looks easy enough to half. Just do the math and see if you are comfortable. Weighing would be best, though. 

A bit extra won't hurt if you have it budgeted. You can always bake them as cupcakes, and freeze,  so you have a midnight snack!

ACan you use tub shortening for buttercream?

Tub shortening - you mean something like Crisco? I use half Crisco, half butter, when I make buttercream.

AIts great value. My husband brought it home. Usually I've used sticks of shortening

Sticks can be convenient, but, you're right, large tubs are a much better value.