Does anyone have a chart/guide or could just give me a rough idea on how much fondant is needed to cover different sizes of cake? i always guess without success! i urgently need to know the quantity to cover 14" 12" and 8" all being about 3 1/2 inch tall.
TIA katie.

Check out Wilton.com

I figured you will need about 10 -12 lbs. Hope this helps.

Here's another source:

http://www.globalsugarart.com/?id=24

Thank you everyone! you have been really helpful.