Originally Posted by muscrat
If that's the folded card size then you start with paper that is 11x11 and score at 4 1/2". That's a pretty large card, so I am assuming you are trying to get an envelope for it folded. You would just follow the A2 measurements for a folded card from that size paper.
My card fronts are normally 8 1/2 by 5 1/2. And yeah you basically need 12 x 12 paper to cut down. Don't know rhe the exact measurements atm as away from my desk.