Curtain Size Calculator
Calculate the recommended curtain width and length for your windows. The calculator accounts for fullness, overlap, and proper hanging height to ensure your curtains look professional and provide adequate coverage.
Recommended Curtain Dimensions
How the Curtain Size Calculator Works
Made-to-measure curtains fail in two ways: panels too narrow to close with any fullness, or lengths that hover awkwardly above the floor. The calculator prevents both by working from the rod, not the window.
Panel width = (rod width ÷ 2) × fullness · Rod width = window + ~35 cm side extension
Curtains hang from a rod that should extend 15–20 cm beyond the window frame on each side — this lets open curtains stack against the wall instead of blocking glass, and makes the window look larger. The fullness factor is what gives curtains their gathered drape: flat panels exactly as wide as the rod would look like bedsheets. A factor of 2 (panels totalling twice the rod width) is the standard for most fabrics. Length is then calculated from your chosen style — sill, apron (15 cm below sill), floor, or puddle (a couple of centimeters pooling on the floor) — and your mounting position.
How to Measure Windows for Curtains
Use a metal tape measure — fabric tapes stretch and lie. Measure the window's full width including the frame, then decide the mounting before anything else, because every other number depends on it: rod above the frame (the default), inside the frame (for recessed windows), or at the ceiling (which makes low rooms look taller).
For height, mount the rod 10–15 cm above the window frame, or two-thirds of the way between frame and ceiling if the gap is large. Measure from the rod's position down to your chosen end point — sill, below sill, or floor — at both ends of the window; floors and ceilings are rarely parallel, and a curtain cut to a single measurement can betray a 2 cm slope across a wide window.
Measure every window separately even when they look identical — in most homes they aren't. And think of curtains together with the wall they occupy: full-height curtains behave visually like wall art, so if the same wall carries pictures, size them together with the wall art calculator. Darker rooms may also want the extra lumens accounted for in our lighting calculator once heavy curtains go up.
Fullness Factor by Curtain Style
| Style | Fullness | Effect |
|---|---|---|
| Relaxed / minimal | 1.5× | Light gathering, modern look |
| Standard pleat | 2× | The default for most fabrics |
| Pencil pleat | 2.25–2.5× | Dense, classic gathering |
| Sheers / voiles | 2.5–3× | Soft fabric needs more volume |
Common Mistakes to Avoid
- Hanging the rod at frame width — curtains then cover glass even when open.
- Skipping fullness and ordering flat panel widths that look like stretched bedsheets.
- Measuring one window and ordering for all of them.
- Choosing floor length but measuring to the sill (or vice versa) — decide the style first.
Frequently Asked Questions
How wide should curtains be for my window?
Total curtain width should be 2 to 2.5 times the rod width, split across two panels — and the rod itself should extend 15–20 cm beyond the frame on each side. For a 150 cm window that means a rod around 185 cm and panels of roughly 185 cm each at 2× fullness.
Should curtains touch the floor?
For most rooms, yes — floor-length (ending about 1 cm above the floor) is the standard that looks tailored. Sill length suits kitchens and radiator walls. Puddling, with a few extra centimeters resting on the floor, is a deliberate romantic look that needs regular re-arranging.
How high should I hang a curtain rod?
10–15 cm above the window frame is the baseline. If there's generous wall above the window, go higher — up to two-thirds of the gap toward the ceiling, or ceiling-mounted entirely. Higher rods make windows look taller and let more light in when curtains are open.
How much fabric do I need for sheer curtains?
Sheers need more fullness than solid fabric — 2.5 to 3 times the rod width instead of the standard 2. Their translucency shows every gap in the gathering, so generous volume is what makes them look soft rather than skimpy. Select the sheer fullness option in the calculator.