Calculate curtain width, length, and fabric needed based on window measurements and fullness.
Fabric is sold by the yard and cut from a bolt of fixed width, so the number that matters is never the window width alone. This calculator turns a window measurement into what an order actually needs: the finished width of each panel, the flat width that a chosen fullness requires, how many fabric widths to cut, the cut length with hem and heading allowances, and the total yardage rounded up to a whole yard. The step people misjudge most is fullness: a 60-inch window gathered at 2x takes 120 inches of flat fabric.
A concrete input and expected output from the current implementation.
Input
Window: 60 in wide, 72 in tall. Fullness: 2x. Two panels. Fabric 54 in wide. Hem 4 in, heading 3 in, no pattern repeat.
Expected output
Finished width per panel: 30 in. Flat fabric per panel: 60 in. Fabric widths needed: 3. Cut length per width: 79 in. Fabric to buy: 237 in = 6.58 yd, rounds up to 7 yd.
Each panel finishes at half the window (30 in) but is cut at 2x fullness, so one panel needs 60 in of flat fabric and the pair needs 120 in - 2.22 widths of 54-in fabric, rounded up to 3 widths. Each of the 3 widths is cut at 72 + 4 + 3 = 79 in, giving 237 in, and 237/36 = 6.58 yd rounds up to 7 whole yards.
The window width is split into two panels, then each half is multiplied by the fullness ratio you choose: about 1.5 for a tailored look, 2 for standard gathers, 2.5 for dense, opulent bunching. The result is the flat fabric width per panel. The finished, gathered panel still covers half the window; fullness only changes how much cloth bunches behind the rod.
The flat width per panel, doubled for two panels, is divided by the fabric's bolt width - 54 inches for decorator fabric, wider for sheers - and rounded up to a whole number of widths. Each width is cut at the finished length plus hem and heading allowances; a patterned fabric adds one full repeat to every cut. Widths times cut length, divided by 36, rounds up to the next whole yard.
Because the window is split into two panels and each gathers at 2x fullness. One panel finishes at 24 inches but needs 48 inches of flat fabric, nearly filling a single 54-inch width, so the pair takes two widths. Comparing fabric width to window width instead of half the window times fullness is the classic reading error.
No. Blinds are rigid panels sized to fit a mount or opening, so their width and length follow the frame and its clearance rules, not a fullness ratio; gathered fabric is the only case where width must exceed the window on purpose. If the window is getting blinds instead, measure inside versus outside mount and the hardware's required clearance rather than applying a fullness figure.
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