How this instrument works
Curtain length follows one of a few common conventions depending on the look and function you want. Standard (also called sill or floor-length) curtains run from the rod down to somewhere around the windowsill or floor, and their length is simply the window height plus however far above the window frame the rod is mounted. Café curtains cover only the lower half of a window, hanging from a middle rod for privacy while still letting light in through the top. Extra-long (puddle-style) curtains deliberately run past floor length by several inches, pooling slightly on the floor for a more formal, dramatic look.
Width works independently of length and is governed entirely by fullness: window width multiplied by a fullness ratio (typically 2x to 3x) so the fabric has enough volume to gather or pleat properly when drawn, rather than hanging flat and skimpy at exactly the window's width.
Rod height above the window frame matters more than it might seem — mounting the rod noticeably higher than the frame is a common styling trick to make a window (and by extension the whole wall) look taller, and because standard-length curtains are calculated as window height plus rod height, raising the rod directly lengthens the curtain you need to order or sew.
- Measure your window's height and width in inches.
- Choose a curtain style: standard/floor-length, café, or extra-long.
- Enter how high above the window frame the rod is mounted (0 if it sits right at the frame).
- Choose a fullness ratio for the width — 2x, 2.5x, or 3x.
- Read the recommended curtain length and width.
Worked example — a standard floor-length curtain
A 48-inch-tall, 36-inch-wide window, standard style, rod mounted 4 inches above the frame, 2x fullness: length = 48 + 4 = 52 inches, width = 36 × 2 = 72 inches. That's the finished panel size to sew or order for a clean floor-length look.
For comparison, a smaller 30-inch-tall, 24-inch-wide window in café style instead (rod mounted mid-window rather than above it), with a 3-inch rod offset and 2.5x fullness: length = 30 ÷ 2 = 15 inches, width = 24 × 2.5 = 60 inches — a dramatically shorter panel covering only the lower half of the glass, since café curtains solve for privacy and light rather than full coverage, and rod offset doesn't factor into the café-length formula at all.
Questions
How high above the window should I mount the curtain rod?
A common styling guideline is somewhere between 4 and 8 inches above the window frame (or higher, in some modern interior design approaches, up to a foot or more) — mounting higher makes the window and ceiling read as taller, and lets the curtain fabric fully clear the glass when opened rather than blocking part of the view. Very low placement, close to the frame itself, tends to visually shrink a window rather than flatter it.
What's the difference between puddle-length and extra-long curtains?
Extra-long curtains as used here add a modest 6 inches past standard floor length, enough to just kiss or barely rest on the floor for a soft, finished look without excess fabric bunching. "Puddle" length in a more formal decorating sense usually goes further still, sometimes 6-12+ inches of deliberate excess pooling on the floor — a much more dramatic, high-maintenance look than the extra-long option calculated here.
When should I use café-style curtains instead of full-length?
Café curtains work well anywhere you want daylight through the upper part of a window while blocking sightlines at eye level — kitchens, bathrooms, and street-facing windows on a ground floor are common uses. Because they only cover the lower half of the window, they're also a lower-fabric-cost option than a full floor-length treatment on the same window.
Does this account for the gap between the curtain and the floor?
Standard style is calculated to land right around sill or floor height (window height plus rod offset), so it doesn't build in an intentional gap — if you want curtains that stop noticeably short of the floor as a deliberate design choice, subtract that gap distance from the calculated length yourself before cutting or ordering fabric.
How does fullness ratio actually change the look of the curtain?
A higher fullness ratio means more fabric is packed into the same window width, so the curtain gathers into denser, more numerous folds when drawn and reads as fuller and more luxurious when open. A lower ratio (closer to 1.5x-2x) lies flatter with fewer, wider folds — a simpler, more tailored look that also uses noticeably less fabric.