I have three boxes of pillsbury white cake mix and I cant remember if that will give me 1 11X15 single sheet cake or 1 12X18 single sheet cake! Thanks!

I am not sure how much pillbury cake mix makes but here is a chart to help you
http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-2-inch-pans.cfm

I'm not sure about the 11x15. But you'll get one single layer from a 12x18 with three mixes.

Single layer 12x18, but you can do 11x15 - it will just be taller. Or just use two boxes. If you do use all 3 in the 11x15 make sure and use flower nails or something as a heating core since it will be thicker.

Pillsbury like Betty Crocker make about 4-5 cups of batter depending on the flavor. An 11x15 needs 11 cups for a full 2in layer and a 12x18 needs 14 cups for a full 2in layer.

thanks!!

I am also curious if I could use the cake mix extender recipe. I have everything it calls for, EXCEPT I only have 8oz of sour cream, BUT, I have a container of yoplait light thick and creamy french vanilla yogurt. Do you think I could mix the sour cream and the yogurt and use the extender recipe? I would like to make the 12X18 sheetcake, but I would like it to be tall. Im thinking 3 boxes won't give me enough batter to make a tall 2in 12X18 cake, but if I used 2 boxes and the extender, I would be golden. Any thoughts on this??

I think the extender gives you about two cups more. (The extender for the single cake mix not double.) So that is 7+4+4, which would give you 15 cups. I can't see why you can't mix the sour cream and yogurt. I've made it both ways and it works fine so I don't know why it wouldn't work combined. Doing the extender with two cake mixes will give you 14 cups.

You can do it either way.

so the cake mix extender recipe on this site, are all those additions only for one cake mix?

There are different ones, that is why I asked to see the recipe you are using. The WASC recipe usually has two cakes mixes to the amounts of every thing are doubled. I don't deal with that big of cakes so I generally do single recipes (single cake mix and the 1 cup additions.)

The recipe you posted in the other thread is a single cake mix recipe. So if you are using it with two cakes mixes and want to extend them both, then you would double it.

thanks texas sugar! I need to slow down and pay better attention!