How to Measure
If your doorway has trim: Measure from outside of trim to the outside of trim.
If your doorway has no trim: Measure the width of opening
If your doorway has trim: Measure from the floor to the top of the trim & from the floor to the bottom of the trim.
If your doorway has no trim: Measure from the floor to the top of the opening.
MAKE SURE the side you want the door to slide has at least as much width as the width of the door, and there are no obstructions out more than 1.5″ from the wall (e.g. baseboard radiations, wainscoting caps, etc.)
You will need about 6″ from the bottom of the top opening to the ceiling.