Curtain Width Calculator

About this calculator

This calculator finds the total fabric width needed by multiplying window width by a fullness ratio — typically 1.5× to 3× the track or rod width, depending on fabric weight and gather style — then dividing across the chosen number of panels and adding a hem/seam allowance per panel. Fullness ratio is the drapery-industry term for how much extra fabric is gathered into folds rather than left flat: too little (under 1.5×) looks skimpy when closed, while sheers are often cut at 2.5–3× for a soft, dense gather.

Interior designers and drapery workrooms use this calculation to quote fabric yardage before cutting, and DIY sewers use it to buy the right amount of fabric the first time, since fullness ratio — not just window width — is what actually determines whether finished curtains look full and tailored or thin and flat.