What Length Curtains Does Your Window Actually Need?Enter your window and ceiling measurements and the calculator gives the standard curtain length and panel width to buy.

Rod: 10 to 15 cm above the window frame, up to 30 cm for high ceilings, and 15 to 20 cm beyond each side.

Width: 1.5 to 2.5 times the window width in total, 2 times for most rooms.

Length: sill ends 1 cm above the sill, kiss 1 cm off the floor, break 2 to 3 cm on it, puddle 15 to 30 cm on it.

Between two sizes: buy the longer one and hem it.

The calculator needs JavaScript to run; the guide to measuring for curtains covers the same ground. Planning the floor as well? Try the rug size calculator.