What size curtains should you choose for a window?
By Nassim Hasni, publisher of DecoScale · published
Curtains are twice the width of the window in all, according to the retailer Wayfair, and their rod goes 10 to 15 cm above the frame. In DecoScale's catalogue, 54 curtains out of 55 are taller than 245 cm: under a 250 cm ceiling they must be shortened, and DecoScale tells you by how much.
Try it on my room · First layout free · no card required
What width of curtains for a window?
The retailer Wayfair gives two rules of thumb, without reconciling them. The first: the width of the window plus 30 cm, that is 15 cm on each side, shared among the panels. The second: at least one and a half times the width of the window, and most often double, so the curtains cover the window when drawn. The chart gives the total width for common windows; the larger of the two is the safer.
| Width of the window (cm) | Window + 30 cm (cm) | One and a half times (cm) | Double (cm) |
|---|---|---|---|
| 80 | 110 | 120 | 160 |
| 100 | 130 | 150 | 200 |
| 120 | 150 | 180 | 240 |
| 140 | 170 | 210 | 280 |
| 160 | 190 | 240 | 320 |
Wayfair: total width of all the panels. Inches converted to cm. Page read on 6 October 2026, not checked by DecoScale.
For two panels, divide by two: a 120 cm window takes, at double, two panels at least 120 cm wide. These are an American retailer's rules, read on its page on 6 October 2026; they are not a standard, and DecoScale does not check them.
How high should the curtain rod go?
10 to 15 cm above the window frame. To make the ceiling look higher, 15 to 30 cm above. The source advises buying a slightly longer curtain and adjusting the rod, rather than the reverse. DecoScale does not check the rod.
What length of curtain?
A floor-length curtain stops about 1 cm from the floor, according to the same source; a pooled curtain needs 15 to 30 cm more. So length depends on the rod and the ceiling: the higher the rod, the longer the curtain.
The ceiling limits that height. DecoScale judges a curtain by its height alone: it keeps 5 cm between the top of the curtain and the ceiling, and if the curtain is longer, it does not rule it out: it tells you it needs shortening, because a curtain is hemmed when hung. The chart gives what it announces, by curtain height and ceiling height, which DecoScale estimates from your photos.
| Height of the curtain (cm) | Ceiling at 240 cm: to shorten (cm) | Ceiling at 250 cm: to shorten (cm) | Ceiling at 260 cm: to shorten (cm) |
|---|---|---|---|
| 240 | 5 | fits | fits |
| 250 | 15 | 5 | fits |
| 260 | 25 | 15 | 5 |
| 270 | 35 | 25 | 15 |
| 280 | 45 | 35 | 25 |
| 350 | 115 | 105 | 95 |
Height − (ceiling − 5), rounded up to the next 5 cm: what DecoScale's screen announces, “about”.
That matters because ready-made curtains are long: 54 of 55 in the survey below exceed 245 cm, the height that fits under a 250 cm ceiling.
What sizes of curtains do retailers sell?
The curtains in DecoScale's catalogue measure 140 to 145 cm wide in median depending on the retailer, and 250 to 280 cm tall. The chart gives, per retailer, the smallest, median and largest values surveyed.
| Retailer | Listings | Width min (cm) | Width median (cm) | Width max (cm) | Height min (cm) | Height median (cm) | Height max (cm) |
|---|---|---|---|---|---|---|---|
| Bonsoirs | 22 | 140 | 140 | 140 | 260 | 260 | 350 |
| Madura | 17 | 134 | 140 | 145 | 270 | 280 | 280 |
| IKEA | 9 | 135 | 145 | 210 | 250 | 250 | 250 |
| Sklum | 4 | 140 | 140 | 140 | 260 | 260 | 260 |
| Camif | 3 | 135 | 140 | 145 | 240 | 260 | 260 |
Survey of 6 October 2026 over DecoScale's catalogue; not checked by the retailers.
Dated survey of 6 October 2026 over 55 listings: 59 are filed as “curtain”, 4 are left out for lack of a reliable height, and 15 heights are read from the title (“145x250 cm”), some retailers' feeds publishing only the width. The width is the listing's, per piece. The numbers are uneven: no median across all retailers is given.
What DecoScale checks, and what it does not
DecoScale checks the height of the curtain under the estimated ceiling, and announces “to shorten by about” a number of centimetres rounded up to the next 5. It does not suggest curtains for a room without a window. It does not compare the width of the curtain with that of the window, and judges neither the rod nor the number of panels: read the width on the retailer's page. The plan of the room comes from your photos and two tape-measure dimensions: see the Method page. The other distances of a room are gathered on room layout dimensions; to design a living room: living room design.
Frequently asked questions
What width of curtains for a 120 cm window?
At least 180 cm in all according to Wayfair (one and a half times the window), 240 cm for a usual result (double), shared among the panels.
How high should a curtain rod go?
10 to 15 cm above the window frame, 15 to 30 cm to make the ceiling look higher.
What to do with a curtain too long for my ceiling?
Shorten it: under 250 cm, a 260 cm curtain needs shortening by 15 cm. DecoScale does not rule it out, it announces it, with a value estimated from your photos.
Does DecoScale compare the curtain's width with the window's?
No: it judges the height of the curtain, not its width or its rod.
How tall are the curtains sold?
250 to 280 cm in median depending on the retailer, in the survey of 6 October 2026.