Wrong measurements are the most common reason curtains disappoint: too short, too skimpy, or dragging on the floor. This guide shows you exactly how to measure your window and calculate how much fabric you need for a full, well-proportioned look. You will finish knowing your rod position, panel width, and finished length before you buy anything.
Measure the rod, not the glass
Curtains hang from the rod, so the rod position controls the finished size, not the window opening. Decide where the rod goes first, then measure. A rod set higher and wider than the frame makes a window look larger and lets light in cleanly when curtains are open.
Height of the rod
Mount the rod roughly 10-15 cm above the frame, or halfway between the frame and ceiling for taller rooms. For a dramatic, ceiling-height effect, mount just below the ceiling or crown molding. Higher rods draw the eye up and make ceilings feel taller.
Width of the rod
Extend the rod 15-25 cm past each side of the frame. This “stackback” gives panels somewhere to sit when open, so they clear the glass instead of blocking it. Wider windows need more overhang per side.
Calculate the width of fabric
Flat panels the same width as your window look thin and cheap. You need fullness, meaning the total fabric width is a multiple of the rod width.
| Look | Fullness multiplier |
| Flat, minimal (heavy fabric) | 1.5x rod width |
| Standard, most rooms | 2x rod width |
| Luxurious, sheers | 2.5-3x rod width |
Example: a rod 200 cm wide at 2x fullness needs 400 cm of total fabric width. If each ready-made panel is 140 cm wide, you need three panels (420 cm), not two.
Calculate the length
Measure from the top of where the fabric will start down to your target end point. Where the fabric starts depends on the heading: rings and clips sit above the rod, while rod-pocket and tab tops sit at the rod.
Choosing the drop
- Sill length: ends at the windowsill. Good for kitchens and bathrooms.
- Below sill: about 10-15 cm past the sill. Practical and tidy.
- Floor length: ends about 1 cm above the floor. The most common, clean choice.
- Puddle: 5-15 cm of extra fabric pools on the floor. Elegant but harder to clean.
Add fabric for hems and heading if you sew your own: typically 15-20 cm for the top and 15-20 cm for the bottom hem per panel. Ready-made panels already include these.
A real scenario
A client had a 160 cm living-room window with panels that stopped at the sill and covered only the glass. The room felt boxed in. We moved the rod to 15 cm below the ceiling, extended it to 210 cm total, and switched to floor-length panels at 2x fullness. Same window, same wall color. The window read almost twice as tall, and the panels no longer blocked daylight when open.
Common mistakes and how to fix them
- Measuring the glass instead of the rod. Fix: install or mark the rod first, then measure from it.
- Buying two flat panels for fullness. Fix: calculate total width as a multiple of rod width and buy enough panels.
- Using a cloth tape that stretches. Fix: use a steel tape measure for accuracy.
- Guessing the floor length. Fix: measure the actual drop with the rod in place; floors are rarely level.
- Forgetting stackback. Fix: extend the rod past the frame so open panels clear the glass.
Action checklist
- Decide rod height and mark it above the frame.
- Decide rod width including 15-25 cm overhang each side.
- Measure rod width; multiply by your fullness factor for total fabric width.
- Divide by panel width to get the number of panels.
- Measure the drop from heading start to your chosen end point.
- Add hem and heading allowance if sewing.
- Write down all numbers before ordering.
Conclusion
Get the rod position right, size for fullness, and pick a deliberate length, and your curtains will look tailored instead of accidental. Your next step: install or mark the rod, then take every measurement with a steel tape and write it down before you shop.
FAQ
How high should I hang a curtain rod?
About 10-15 cm above the frame, or higher toward the ceiling for a taller effect. The higher the rod, the taller the window appears.
How much wider than the window should curtains be?
Total fabric width should be about 1.5-3 times the rod width, depending on how full you want the look. Two times is a safe standard.
Should curtains touch the floor?
For most living spaces, ending about 1 cm above the floor looks clean and stays out of the way. Puddling is optional and more decorative.
Can I use one wide panel instead of two?
You can, but a single panel only draws to one side. Two or more panels part in the middle and usually look more balanced.
