Curtain size calculator

How the curtain calculator works

The rod comes first. It extends past the window frame on each side, 8 inches (20 cm) by default, so the open curtains cover the wall and not the glass. The rod width is the window width plus both extensions.

Width comes next. Curtains look full when the panels together are about twice the width of the rod. The calculator divides that width by the width of one panel and rounds to a pair, because panels hang one on each side. It then shows the fullness you actually get.

Length comes last. It is the height of the rod above the floor, minus a small gap if you want the curtains to float, or plus a few inches if you want them to pool. The calculator matches that to the nearest standard length and tells you how far to move the rod or hem the panels.

Hang the rod high and wide

The standard rod height is 4 to 6 inches (10 to 15 cm) above the window frame. Hanging it higher, about halfway between the frame and the ceiling, makes the window and the room look taller. A wider rod makes the window look wider and lets in more light when the curtains are open.

Measure from the rod to the floor when the rod is up. If you use rings, measure from the bottom of the rings, because the curtain hangs from there. Measure at both ends of the window too: old floors are rarely level.

Standard curtain lengths

Ready-made curtains in the US come in 63, 84, 95, 108 and 120 inch lengths. In Europe and the UK, common lengths are 137, 183, 229, 250, 260 and 280 cm. The calculator only recommends lengths from these lists, so you can buy panels off the shelf.

Choose a length that reaches the floor or floats just above it. Curtains that stop above the sill or halfway down the wall make a window look small. Short curtains suit a window over a radiator, a kitchen counter or a bench seat.