How To Measure For A Barn Door Kit. If your doorway doesn't have a trim, measure the width of the inside of the door frame from left to right. Finally, add one inch to whatever your final measurement was.
Add 1″ to 2″ per door for overlap depending on privacy needs. The rail can be extended by purchasing an extension rail kit. Similarly, if you want to buy a double door hardware kit, then the track length = length of the opening + the width of the left door + the width of the right door + some extra space on both sides (4 to 6 inches).
For door openings with casing/molding:
If you purchase a barn door kit, it likely includes a hardware kit that comes with most of the necessary supplies needed, such as bolts, nuts, washers, and other hardware specific to your door. Take the above measurement of your door and double it. This barn door hardware kit a furniture sliding door hardware system for double doors. If you have trim around your door, you may want to get a barn door that covers your trim completely or allows it to show slightly around your door.