Panel width recommender
Length planner
Rod placement
Standard size matcher
Heading adjuster
Sliding / patio door
Multi-window room planner
How the math works
Rod width: window width + 10″ total (5″ overhang per side), or + 24 cm in metric. This matches the standard designer rule and lands exactly on the common 48″ → 58″ example.
Panel width: rod width × fullness — 1.5× minimum, 2× ideal, 2.5–3× for sheers. Two panels is standard; rods over 88″ get a third panel so the middle does not look under-filled; narrow rods (40″ and under) take a single panel.
Mount height: 5″ above the trim (designer range 4–6″). If the trim-to-ceiling gap is 12″ or less, mount 2″ below the ceiling instead.
Length: sill = rod-top minus sill; apron = sill + 4–6″; floor = rod-top to floor (kiss, or float 1/2″); puddle = floor + 2–4″ subtle or + 6–12″ dramatic.
Headings: rod pocket 0″; grommet −2″ (range 1–2″); pinch pleat on clips −1″; tab top −3″ (range 2–4″).
Standards: widths 50/52/54/60/72/100/108″, lengths 63/84/96/108″. Width matches size up for coverage; length matches nearest.
Sources: Wayfair measuring & hanging guide, Pottery Barn hanging guidance, Homes & Gardens, Temple & Webster. See SOURCES in the project notes. Boundary: this tool sizes ready-made panels to buy. If you plan to sew curtains, use our curtain fabric calculator for yardage, pleat fullness, and pattern repeats. Sizing a rug for the same room? Use our rug size calculator for dining, living room, bedroom, and runner layouts.
Frequently asked questions
What size curtains do I need for a 48-inch window?
For a 48-inch window, buy a 58-inch rod (window width plus 10 inches, 5 inches of overhang per side). At the ideal 2x fullness you need 116 inches of total panel width, which means two panels of 58 inches each — buy two standard 60-inch panels. In metric: a 122 cm window takes a 147 cm rod; at 2x fullness that is 294 cm total, or two 147 cm panels (buy two 150 cm panels).
How wide should my curtain panels be?
Multiply your rod width by 1.5 for minimum coverage or 2 for the ideal full look; sheer curtains need 2.5 to 3 times the rod width. For example, an 84-inch window takes a 94-inch rod, which needs 141 to 188 inches of combined panel width at 1.5x to 2x fullness. If your rod is wider than 88 inches, use three panels instead of two so the stack-back does not swallow the window.
How long should curtains be?
Measure from the top of the rod to your target point. The four classic lengths are: sill length (just above the sill), apron length (4 to 6 inches below the sill), floor length (kissing the floor or floating 1/2 inch above it), and puddle length (2 to 12 inches of extra fabric pooling on the floor). Use the Length Planner tab above to compute each style from your own measurements.
What are the standard curtain sizes?
US ready-made curtain panels most commonly come in widths of 50, 52, 54, 60, 72, 100, and 108 inches, and lengths of 63, 84, 96, and 108 inches. If your computed size falls between standards, size up in width for coverage and pick the nearest standard length — for example, an 85-inch floor measurement takes an 84-inch panel, and a 93-inch puddle measurement takes a 96-inch panel.
How high should I hang curtains?
Mount the rod 4 to 6 inches above the window trim — 5 inches is the standard designer default. With 8-foot ceilings, mounting halfway between the trim and the ceiling also works. If the gap between the trim top and the ceiling is 12 inches or less, mount the rod 1 to 2 inches below the ceiling instead.
How long should my curtain rod be?
Add 10 inches to the window width — about 5 inches of overhang on each side — so the panels can stack off the glass when open. A 48-inch window takes a 58-inch rod. In metric, add 24 cm total (12 cm per side): a 150 cm window takes a 174 cm rod. For heavy or daily-use curtains, add a few extra inches per side for stack-back room.
Should I buy one curtain panel or two?
Two panels (a pair) is the standard for most windows: they meet in the middle and stack evenly on both sides. One wide panel suits narrow windows and one-sided stack looks. For rods wider than 88 inches, step up to three panels — two panels leave an under-filled middle on very wide spans. The Panel tab above applies this rule automatically.
What length curtains do I need for an 8-foot ceiling?
With an 8-foot (96-inch) ceiling and a typical trim top at 80 inches, mount the rod 5 inches above the trim at 85 inches. For floor length that means an 85-inch panel — buy the nearest standard 84-inch panel and let it float just off the floor. If you want a puddle instead, add 2 to 4 inches for a subtle break or 6 to 12 inches for a dramatic pool.
Should curtains touch the floor?
Floor-length curtains should either just kiss the floor or float 1/2 inch above it — never hover several inches short, which looks like a measuring mistake. Puddling is a deliberate style: add 2 to 4 inches of extra length for a subtle break, or 6 to 12 inches for a dramatic pool. Kitchens, bathrooms, and homes with pets usually do better with sill or apron length.
How do different headings change the length I buy?
The heading shifts where the panel hangs relative to the rod. Rod-pocket panels start at the rod, so buy the exact measured length. Pinch-pleat panels on clip rings start about 1 inch below the rod — buy 1 inch longer. Grommet panels need 1 to 2 inches extra (use 2 inches for a safe buy): a listed 84-inch grommet panel hangs at 82 inches finished, so for an 84-inch drop buy an 86-inch panel. Tab-top panels drop 2 to 4 inches below the rod — buy 3 inches longer.
What size curtains do I need for a sliding glass door?
Treat the door like an extra-wide window: rod width is the door width plus 10 inches, fullness 2x for an ideal look, and floor or puddle length. A 72-inch sliding door takes an 82-inch rod with 164 inches of total panel width — two 82-inch panels (buy two 100-inch standards) or four narrower panels for easier daily sliding. Add stack-back room if the door is used constantly.
How do I measure curtains in centimeters?
The same rules apply in metric: rod width is the window width plus 24 cm (12 cm per side), and fullness is still 1.5x to 2x (sheers 2.5x to 3x). A 150 cm window takes a 174 cm rod; at 2x fullness that is 348 cm of total panel width, or two 174 cm panels. Switch to Metric in any tab and all results convert automatically.
What length is a sill-length kitchen curtain?
Sill length is the rod-top height minus the sill height, ending just above the sill. For example, if your rod top sits at 70 inches and the sill is at 16 inches, buy a 54-inch panel. Apron length for the same window would be 58 to 60 inches (4 to 6 inches below the sill).
Is this different from a curtain fabric calculator?
Yes. This tool answers the buying question — what finished panel width and length to purchase and where to mount the rod. A curtain fabric calculator answers the sewing question — how many yards of raw fabric to buy to make those panels, including pleat fullness and pattern repeats. If you plan to sew your own, use our curtain fabric calculator after sizing here.
What size curtains for an 84-inch wide window?
An 84-inch window takes a 94-inch rod (84 plus 10). At 1.5x minimum fullness you need 141 inches of combined panel width; at 2x ideal fullness you need 188 inches. Because the rod is wider than 88 inches, use three panels: about 47 to 63 inches each — buy three 50-inch standards for lean coverage or three 72-inch standards for the full look.
How do I measure for curtains?
Measure in three steps. First, measure the window width, then add 10 inches (5 inches per side) for the rod: a 48-inch window takes a 58-inch rod. Second, decide the finished length: measure from the rod top to the sill (sill length), 4 to 6 inches below the sill (apron length), or the floor (floor length, floating 1/2 inch above it). Third, multiply the rod width by 1.5 to 2 for panel fullness: a 58-inch rod needs 87 to 116 inches of combined panel width. Always use a steel tape measure and measure twice.
Do I measure the window or the rod for curtain width?
Measure the rod for the width math, and the window for the rod math. First size the rod from the window (window width plus 10 inches, or 20 percent longer per Wayfair's guide — both give a 58-inch rod for a 48-inch window). Then multiply the rod width by your fullness: a 58-inch rod at 2x needs 116 inches of panel. Pinch-pleat headings have about 2x fullness built in, so buy panels to roughly the rod width.