How to Measure Stack for Traverse Curtain Rods

Measure the width of the window, or the area to be covered, from left to right; outside frame to outside frame.

Decide how the curtains will open. The three options are: all to the left, all to the right, or center spilt with half stacking right, half left. Consideration should be given to adjacent walls, light switches, floor registers and the direction of door openings, if applicable.

Determine the type of drapes for the window. Curtains are single-layered window coverings and, typically, are constructed to two and one-half to three times fullness. Fullness is the ratio of window width to the fabric before construction. Drapes are curtains with lining and are typically constructed from two to two-and one-half times fullness. If the drapes are blackout-lined and interlined, the fullness is rarely more than two- and one-half times. Sheers are rarely less than three times fullness, but are not lined. The more fabric and bulk in the curtains, the more room they require for stack back.

Calculate 20 percent of the window width for curtains that are either up to two- and one-half times fullness in a light to medium-weight fabric or sheers at three times fullness. For example, if the window is 100 inches wide, the curtains, at minimum fullness and of a light-weight fabric, will require 20 inches for stack back for a center split; 10 inches on each side of the window. The rod required would be 120 inches long. If the system is to be one-way draw, the minimum required would be 20 inches on the stack-back side, and an additional 6 inches on the other side for clearance. The total rod length would be 126 inches.

Calculate 25 percent of the window width for curtains that are lined or of higher fullness. For example, a window of 100 inches, with drapes at two- and one-half times fullness and lined with blackout lining, would require a rod 125 inches wide for center split and 131 inches for a one-way draw.