Curtain Panel Calculator

Curtain yardage is worked out in two independent directions. Across the window, finished width is the rod or window width multiplied by a fullness factor: 1.5 times gives a flat modern look, 2 times is the standard for pleated and pinch-headed panels, and 2.5 to 3 times is used for sheers and formal treatments, because thin fabric needs more gathering before it reads as full. That total is divided among the panels and then divided by the fabric bolt width to give whole fabric widths, always rounded up, since a shortfall must be seamed rather than stretched. Decorator goods are commonly 54 inches wide, with 45, 48, and 60 inch bolts also in circulation, while sheers and linings are often woven at 110 to 118 inches. Down the window, cut length is the finished drop plus allowances. The finished drop runs from the rod to the chosen end point: the sill, 4 inches below the sill, half an inch above the floor, or 2 to 6 inches puddled on it. To that add the bottom hem, conventionally 8 inches to allow a 4 inch double fold, and a header allowance set by the heading style, roughly 3 to 4 inches for a rod pocket, 4 to 6 for grommets, and 8 to 10 for pinch pleats. Patterned cloth needs one extra pattern repeat per cut length so the motif aligns across panels, so add 10 to 15 percent beyond the calculated total and buy from a single dye lot.

Fabric bolt widths, which drive the entire width calculation, are inherited from the loom. Hand looms were limited by how far a weaver could throw a shuttle, so cloth stayed narrow until John Kay's flying shuttle of 1733 and Edmund Cartwright's power loom of 1785 made broader, consistent weaving practical. The 54 inch width that still defines decorator fabric descends from those mechanised broadloom standards, and it is the reason any panel wider than about 54 inches has to be seamed from multiple widths rather than cut in one piece. Fullness rules and heading allowances come from the upholstery and drapery workroom trade rather than from any published standard. Elaborate window hangings were a status feature of eighteenth and nineteenth century interiors, and the pattern books issued by cabinetmakers and upholsterers of that era illustrated the pleated, swagged, and festooned treatments whose proportions were later codified as simple multipliers. Mass-market curtain making then depended on hardware: the flat metal curtain rod and the traverse rod developed by the Kirsch company of Sturgis, Michigan, from around 1907 made hanging and drawing pleated panels practical in ordinary houses. Pattern repeat allowance became a routine part of estimating once roller printing put large-scale repeating designs onto affordable furnishing cloth during the nineteenth century.