How to measure for curtains
Designers hang curtains higher and wider than the window itself. It makes ceilings look taller and windows look bigger, and when the curtains are open they stack on the wall instead of blocking the light. The calculator follows the same rules.
- Measure the window width from the outside edge of the frame on one side to the other.
- Add 8 to 12 inches (20 to 30 cm) on each side for the rod, so the stacked curtains clear the glass.
- Place the rod 4 to 6 inches (10 to 15 cm) above the frame, or about halfway between the frame and the ceiling if the space is tight.
- Measure from the rod down to the floor and adjust for how you want the fabric to fall.
The curtain size formula
Four lines do all the work. The calculator runs exactly these, in inches or centimeters:
Rod height = top of the frame + 4 to 6 in (10 to 15 cm), or half the gap to a low ceiling
Rod width = window width + 2 × side extension, where each side gets 20% of the window width, kept between 8 and 12 in (20 and 30 cm)
Curtain length = rod to floor, then adjust for float, kiss, break or puddle
Panels = rod width × fullness ÷ width of one panel, rounded up to an even number
Worked example. A 48 in window whose frame top sits 84 in above the floor, with 12 in up to the ceiling. The rod goes 6 in above the frame, so rod to floor is 84 + 6 = 90 in, and kissing the floor means curtains 90 in long. Buy the next standard length, 95 in, and hem 5 in. Each side extension is 20% of 48, so 9.5 in, and the rod is 48 + 2 × 9.5 = 67 in. At standard 2x fullness that is about 134 in of fabric, and 134 ÷ 52 in panels = 2.6, which rounds up to 4 panels, or 2 pairs.
Worked examples: real windows, real results
Every row below is the calculator's own output for that window, using 52 in panels unless noted.
| Window | Frame top to floor, space above | Fall and fullness | Curtain length | Buy | Rod and panels |
|---|---|---|---|---|---|
| 36 in, 8 ft ceiling | 80 in, 16 in | Kiss, 2x | 86 in | 95 in, hem 9 in | 52 in rod, 2 panels |
| 36 in, 9 ft ceiling | 80 in, 28 in | Kiss, 2x | 86 in | 95 in, hem 9 in | 52 in rod, 2 panels |
| 48 in, 8 ft ceiling | 84 in, 12 in | Kiss, 2x | 90 in | 95 in, hem 5 in | 67 in rod, 4 panels |
| 48 in, formal | 84 in, 12 in | Puddle, 2.5x | 97 in | 108 in, hem 11 in | 67 in rod, 4 panels |
| 72 in sliding glass door | 80 in, 16 in | Kiss, 2x | 86 in | 95 in, hem 9 in | 96 in rod, 4 panels |
| 72 in picture window | 84 in, 12 in | Float, 2x | 89.5 in | 95 in, hem 5.5 in | 96 in rod, 4 panels |
| 60 in, 10 ft ceiling, sheers (54 in panels) | 96 in, 24 in | Kiss, 3x | 102 in | 108 in, hem 6 in | 84 in rod, 6 panels |
| 30 in kitchen window, 36 in tall (46 in panels) | 48 in, 10 in | Sill, 1.5x | 40.5 in | 45 in, hem 4.5 in | 46 in rod, 2 panels |
| 120 cm window (140 cm panels) | 210 cm, 30 cm | Kiss, 2x | 225 cm | 229 cm, hem 4 cm | 168 cm rod, 4 panels |
Notice that the 8 ft and 9 ft rooms come out the same: the rod stays 6 in above the frame either way. In a tall room you can mount it higher for drama. Just add the extra height to the frame top to floor measurement so the curtains still reach the floor.
How long should curtains be for 8, 9 and 10 foot ceilings?
Most US windows have the frame top about 80 in above the floor. With the rod 6 in higher, that is 86 in to the floor, so 95 in panels hemmed a few inches suit most 8 ft and 9 ft rooms. If you hang the rod close to a 9 ft ceiling instead, measure rod to floor and you will usually land on 102 to 106 in, which means 108 in panels. In a 10 ft room with tall windows, 108 in or 120 in panels are the usual buy. 84 in panels only work when the rod sits low, which is the most common reason curtains end up looking too short.
Curtains for a sliding glass door
Treat a patio door like a wide window, and give it a little extra on the side the door opens so the fabric stacks fully clear of the glass. A standard 72 in door needs a rod of about 96 in. At 2x fullness that is 4 panels of 52 in, and most doors take 95 in panels hemmed to just kiss the floor. Avoid puddling here, because the fabric drags every time the door slides.
Curtain lengths: float, kiss, break or puddle
| Style | How it looks | Adjust the length |
|---|---|---|
| Float | Hovers just above the floor, clean and practical | About 1/2 in (1 cm) shorter than rod to floor |
| Kiss | Just touches the floor, the most tailored look | Exactly rod to floor |
| Break | A slight bend where the fabric meets the floor | Add 1 to 2 in (3 to 5 cm) |
| Puddle | Pools on the floor, romantic and formal | Add 6 to 8 in (15 to 20 cm) |
Standard ready made lengths are 63, 84, 95, 108 and 120 inches in the US, and around 160, 213, 229 and 250 centimeters elsewhere. If your ideal length falls between two, buy the longer panel and hem it, or use clip rings to adjust the drop.
How many curtain panels do I need?
Curtains look best when the fabric is about twice as wide as the rod, so they fall in soft folds even when closed. Multiply the rod width by the fullness you want, then divide by the width of one panel and round up to an even number so you have matching pairs. Sheers need more, up to three times the rod width, because thin fabric looks skimpy when stretched flat.
For styling ideas, see our bedroom decor ideas and living room decor ideas, and match your fabric with the color palette generator.
