Preparing to buy ready-made curtains can be exciting for a new homeowner, or even if you are just redecorating a room. Before you can buy, however, you’ll want to measure so you know how large your window is and where you would like for the curtain to fall. Once you have measured, you shouldn’t need to do anything else other than select a ready-made curtain in your favourite pattern as close to your window size as possible.
Measure the width of your curtain rod from end to end, not including any finials or other decorative end pieces. Multiply this number by 1.25 for a minimal amount of folds in the curtain; by 1.5 for a moderate amount of folds; or by 1.75 for a lot of fold in the curtains.
Divide that number by 2, and add an extra 2.5 cm (one inch) to that number. This is the approximate width you want to purchase in your ready-made curtains.
Measure from your curtain rod down to where you want the curtains to fall in relation to the window. Most curtains rest at one of three places: above the sill, just below the sill or to the floor. See the "Tips" section for more information on measuring the length of the curtain.
Find a curtain that best matches the width you determined in step two and the length needed from step three. Most ready-made curtains come in widths of 117, 168 and 229 cm (46, 66 and 90 inches), and in lengths including 137, 183, 229 and 274 cm (54, 72, 90 and 108 inches); other sizes may be available, depending on the manufacturer.
For a curtain that stops just above the sill, measure to within 1 cm (around a half-inch) of the window sill. For a curtain to extend to just below the sill, measure the distance to 15 cm (six inches) below the window sill. For curtains that fall to the floor, measure down to within 1 cm (around a half-inch) from the floor.
A rough guideline for your ready-made curtains without doing any maths is to purchase the curtain size width which is closest to the length of your curtain rod. A 120 cm (48 inch) long curtain rod would therefore use 115 cm (46 inch) wide curtains.