OneTaskBy Tim King · Updated
Curtain Size Calculator
Width, Drop and Fabric for Any Window
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How the Curtain Size Calculator works
This curtain size calculator works out the width and drop you need for a window. Enter the window width, the drop from the track or pole to where the curtain should finish, how far the track extends past the window and the heading style, and it returns the track length, the gathered fabric width, the ready-made width to buy and the finished drop.
Curtains are wider than the window because the heading gathers the fabric into folds. The amount of gathering is the fullness: pencil pleat and pinch pleat need about 2.25 times the track length, wave about 2, eyelet about 1.75 and tab top about 1.5. Too little fullness and the curtains look flat and will not close; too much and they stack up in front of the glass when open.
How the curtain size calculator works
The formula is track length = window width + 2 × extension, and fabric width = track length × fullness. For example, a 150 cm window with a 15 cm extension each side has a 180 cm track; in pencil pleat that is 180 × 2.25 = 405 cm of fabric, or 203 cm per curtain for a pair. A second example in inches: a 60 in window with 6 in each side is a 72 in track, and eyelet curtains need 72 × 1.75 = 126 in of fabric, 63 in per curtain.
Ready-made curtains are sold by their ungathered width, so buy a pair where each curtain is at least the track length divided by two times the fullness the maker recommends; most makers simply list "fits a track up to" a width. For the drop, measure from the top of the track or the bottom of the pole rings to the finish point: 1 cm above the sill, 1 cm above the floor for a full-length curtain, or a few centimetres onto the floor for a puddled look.
To work out how many metres of fabric a made-to-measure curtain uses, multiply the number of fabric widths by the cut drop (finished drop plus about 25 cm for hems and heading).
Track length and gathered fabric width by window width (15 cm extension each side)
| Window width | Track length | Pencil or pinch pleat (2.25×) | Wave (2×) | Eyelet (1.75×) |
|---|---|---|---|---|
| 60 cm | 90 cm | 202 cm | 180 cm | 158 cm |
| 70 cm | 100 cm | 225 cm | 200 cm | 175 cm |
| 80 cm | 110 cm | 248 cm | 220 cm | 192 cm |
| 90 cm | 120 cm | 270 cm | 240 cm | 210 cm |
| 100 cm | 130 cm | 292 cm | 260 cm | 228 cm |
| 110 cm | 140 cm | 315 cm | 280 cm | 245 cm |
| 120 cm | 150 cm | 338 cm | 300 cm | 262 cm |
| 130 cm | 160 cm | 360 cm | 320 cm | 280 cm |
| 140 cm | 170 cm | 382 cm | 340 cm | 298 cm |
| 150 cm | 180 cm | 405 cm | 360 cm | 315 cm |
| 160 cm | 190 cm | 428 cm | 380 cm | 332 cm |
| 170 cm | 200 cm | 450 cm | 400 cm | 350 cm |
| 180 cm | 210 cm | 472 cm | 420 cm | 368 cm |
| 190 cm | 220 cm | 495 cm | 440 cm | 385 cm |
| 200 cm | 230 cm | 518 cm | 460 cm | 402 cm |
| 210 cm | 240 cm | 540 cm | 480 cm | 420 cm |
| 220 cm | 250 cm | 562 cm | 500 cm | 438 cm |
| 230 cm | 260 cm | 585 cm | 520 cm | 455 cm |
| 240 cm | 270 cm | 608 cm | 540 cm | 472 cm |
| 250 cm | 280 cm | 630 cm | 560 cm | 490 cm |
| 260 cm | 290 cm | 652 cm | 580 cm | 508 cm |
| 270 cm | 300 cm | 675 cm | 600 cm | 525 cm |
| 280 cm | 310 cm | 698 cm | 620 cm | 542 cm |
| 290 cm | 320 cm | 720 cm | 640 cm | 560 cm |
| 300 cm | 330 cm | 742 cm | 660 cm | 578 cm |
FAQ
How wide should curtains be for a window?
Each curtain in a pair should be at least the track length when gathered, which usually means an ungathered width of 1.5 to 2.5 times half the track. For a 180 cm track a pair of curtains each about 200 cm wide flat will look full and close properly.
How far past the window should a curtain pole go?
Extend the track or pole 15–20 cm (6–8 in) past each side of the window frame. That lets the curtains stack clear of the glass when open, so they block less daylight, and it helps them overlap the frame when closed to stop draughts and light leaks.
What is the difference between eyelet and pencil pleat curtains?
Eyelet curtains have rings punched through the fabric and slide straight onto a pole, forming even, deep folds with about 1.75 times fullness. Pencil pleat curtains have a tape that you draw up with cords and hang on hooks from a track or pole, and need a little more fabric.
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