Remove the old closet door from the closet opening. Measure the length and width of the finished opening.
Select a bifold door which is approximately 1 inch less than the width of your closet opening and 1 to 2 inches less than the height of your closet opening. Combine the widths of the bifold doors if you are installing two.
Purchase a bifold door slightly larger than your closet opening and plan to cut it to the proper length if the size door you need is not available.