I need to simply cover an 8" cake with white chocolate ganache.  Most of the recipes/ratios I've seen are for larger batches of ganache.  Can anyone suggest how many ounces of chocolate and cream I would need to ice the cake with?  I am filling with buttercream so it just needs to be enough to cover the outside.  I will most likely be using bar chocolate because I'm not big on using chips for ganache, but I have never made white chocolate ganache so I am open to any suggestions. 

Thanks!

I always use a 3:1 ratio by weight.
 

I couldn't find a lot info on this but I just read someone used about 8 oz of chocolate for covering an 8 inch cake.so you need 2.6 oz of cream to make the ganache.  I always make larger batch and freeze the rest.
 

Thanks!  I appreciate the info.

This is called white chocolate butter cream, but it's really white whipped ganache...and it's a fabulous recipe!!! Just double the recipe :) I've covered a ten inch cake with it.

http://cakecentral.com/a/white-chocolate-buttercream-2

Thanks for the recipe!

http://cakecentral.com/t/741743/the-ganacherator

Woot!  Thanks Spooky!

You're welcome!  I've saved the calculator for future use as I've asked this question before and no one ever had an answer so I had to wing it.  Love it when folks create something and are willing to share with others.