How the curtain calculator works
Enter the size of your window, the height of your ceiling and how you want the curtains to hang. The calculator works out where to mount the rod, how long it should be, the finished length of each panel and how many panels you need to look full rather than flat. It also shows ready-made lengths near your result and how much to hem.
- Floor length curtains hang from the rod to the floor. Choose float, kiss, break or puddle for the finish.
- Apron length curtains end about 4 in (10 cm) below the window sill. They suit kitchens and rooms with radiators or furniture under the window.
- Sill length curtains end at the sill. They are the tidiest choice above a sink or desk.
The curtain rules the calculator follows
| Measurement | Rule of thumb |
|---|---|
| Rod height | 4 to 6 in (10 to 15 cm) above the window frame as standard. For a taller look, hang it halfway to the ceiling or just below it. |
| Rod width | Window width plus 8 to 12 in (20 to 30 cm) on each side, so the curtains stack beside the glass and let in the full light. |
| Fullness | 1.5× the rod width at the minimum, 2× for a standard look, 2.5× or more for sheers and pleated styles. |
| Float | About ½ in (1 cm) above the floor. Easy to keep clean. |
| Kiss | Just touching the floor. A crisp, tailored line. |
| Break | 1 to 2 in (3 to 5 cm) of extra fabric that bends where it meets the floor. |
| Puddle | 3 to 6 in (8 to 15 cm) of extra fabric pooling on the floor. Dramatic, best for lightweight fabric and low-traffic rooms. |
How to measure for curtains
- Measure the window frame (casing) from outer edge to outer edge for the width.
- Measure from the floor to the top of the frame, and the height of the window itself.
- Measure the ceiling height. If the window sits close to the ceiling, the rod may have to go lower than you wanted.
- Check the curtain top style. Clip rings hang the fabric about 2 in below the rod, while a rod pocket has a heading above the rod. This changes the length you need to buy.
- Read the panel width on the packaging. Ready-made panels are usually 50 to 54 in (127 to 137 cm) wide.
Standard curtain lengths
| Ready-made length | Metric | Typical use |
|---|---|---|
| 36 to 54 in | 91 to 137 cm | Sill and apron length, kitchens, bathrooms |
| 63 in | 160 cm | Standard windows hung low, café curtains |
| 84 in | 213 cm | Floor length with a standard 8 ft ceiling and a rod 4 to 6 in above the window |
| 95 to 96 in | 240 to 245 cm | Floor length with a higher rod or a 9 ft ceiling |
| 108 in | 274 cm | Floor length on 9 ft ceilings with a high rod |
| 120 in | 305 cm | Tall ceilings of 10 ft or more |
Ready-made panels can be shortened but not lengthened. When you are between sizes, buy the longer one and hem it up.
Worked examples
Standard window, 8 ft ceiling
A window 36 in wide and 48 in tall, with the top of the frame 78 in from the floor and a 96 in ceiling. With the rod 4 in above the frame, it sits at 82 in (6 ft 10 in) and runs 56 in wide. Floor-length panels that just kiss the floor need a finished length of about 80 in when hung from clip rings. Buy 84 in panels and hem them up 4 in. At 2× fullness you need 112 in of fabric, which is four 50 in panels.
Making a room feel taller
Raise the rod to 4 in below a 9 ft ceiling and the same window needs panels about 102 in long. A 108 in panel hemmed up 6 in does the job, and the room looks noticeably taller.
Kitchen window
Switch to apron length. The same window’s curtains end 4 in below the sill, so they stop at roughly 54 in. A ready-made 54 in panel fits as it comes.
Common curtain mistakes
- Hanging the rod right on the frame. It makes the window look smaller and blocks light when the curtains are open.
- Rods that are too short. A rod that stops at the frame means the curtains cover the glass even when open.
- Too little fabric. Panels stretched flat at 1× look thin. Aim for 2× the rod width.
- Measuring to the floor and forgetting the hardware. Rings and hooks change the finished length by an inch or two.
- Curtains that stop above the floor by a few inches. They look like a mistake. Go to the floor, or go clearly short with sill or apron length.
Tips for better-looking curtains
- Use a wider rod than you think you need. It is the cheapest way to make a window look larger.
- Steam or iron the curtains after hanging, so the hem falls straight.
- Hang curtains for a day before you hem them, because the fabric can drop a little.
- For a ceiling that is not level, measure the length at both ends of the window and use the shorter.
- Choose lined or blackout panels for bedrooms, and lightweight fabric for puddles.
