We created 2 different stackback calculators. The first one is to determine the rod/track width depending on the window width if you want to clear the entire window when the curtains are drawn the to sides, and the second one to figure out the stackback width given the track width. The second calculator (stack back) is more precise.
This calculation is providing an estimated rod width given the window width, to have the entire windows uncovered when the drapes are drawn open fully.
*Please note that the calculation of the stack back width is only an estimate, stack back can fluctuate depends on factors such as puddling, fabrics, lining options, curtain rods, brackets, and rings.*