I'm just getting started as a "professional baker", I'm used to making smaller 8"-9" layer cakes but never anything larger than that. my question is, if I were making like a wedding cake or something requiring 12" or greater how do I make enough batter to make sure I can fill the pans? Are the special recipes for larger quantities or do i double my standard 9" recipes which i'm thinking would affect the quality of the cake and flavor. Please help

I have always just doubled my recipes for larger cakes! or triple!
 

It will probably vary depending on the cake you're making too. Some batters are a lot thicker than others and rise differently. Might have to do some experimenting before you get it perfect.

Thank you all for the advice and for making this site such a pleasant resource for beginners and experts.