How many boxed mixes should I use for this size pan?

Thank you

I don't remember but I think I used 1 box mix WASC recipe for one 12 inch pan.

For my comm'l convection oven: 2 Betty Crocker's for round; 2.5 for square

When I baked in a home oven, I could decrease the batter by 1/2 mix for each.

I use 2 for this.