How to measure for a barn door in three steps.
Barn door measurements.
Sheetrocked opening no trim or casing width.
Measure across for the width and from the top of the casing molding to the floor for height.
Measure from outside to outside of casing molding.
Add 1 to 2 per door for overlap depending on privacy needs.
If the doorway has moldings measure from outside edge to outside edge to determine the proper door width add about 4 to 6 inches to your measurement.
Do this by measuring from the left to the right side of the door.
Most barn door sizes fall anywhere between 36 wide on the shorter side by 96 tall on the longer side.
Add 4 to the measurement and you have your recommended door width.
In this example the opening width is 32 4.
Barn door measuring guide for door openings with casing molding.
Barn door opening measurements while the style of barn door you choose will come down to your personal preference you will need to be aware of barn door vs opening dimensions when making your choice.
Measure the door width.
Generally most standard barn doors are approximately 36 x 84 or 42 x 80 with enough extra lip to overlap most standard door frames 36 x 80 by an inch or so.
Using a tape measure begin at the left edge of the opening and measure straight across to the right edge.
Exterior door sizes may even be larger.
Ideally the door will cover 2 to 3 inches beyond the opening on each side.
Measure from inside to inside of the opening.