Add 2 inches to that number and cut a length of j channel to this.
Installing j channel around windows.
Start j channeling the window from the bottom make cuts on both ends of the j channel.
Check the frame of the window and clean anything that is not gonna allow for a j channel to lay flat to the side of the window.
How do you install j channel around windows.
Cut and install the side j channels.
Place the side j channel and mark it then mark the bottom j channel.