Curtain Size Calculator: What Size Curtains Do I Need?
Measure your window once and see the pole or track length, the width and drop of each curtain, the nearest ready-made size in inches or cm, and how many metres of fabric you need to make them yourself.
No sign-up required. Free to use, with every formula shown on this page. Last reviewed October 2026.
Work out your curtain size
Curtain Size Calculator
Measure your window once and see the pole length, the curtain width and drop to buy, the nearest ready-made size, and how much fabric you need to make them yourself.
1 Your window
Measure inMeasure the outside of the frame (or the recess), and the height from the top of the frame to the sill.
Only needed for floor-length curtains. For a door or a floor-to-ceiling window, enter 0 and measure the window height to the floor.
2 Pole or track
Hanging from15 to 20 cm each side lets the open curtains clear the glass. Fitting the pole higher and wider makes the window look bigger.
3 Your curtains
Heading (the top of the curtain) LengthThe drop is the length of the curtain, from the pole or track to the bottom hem.
4 Making them yourself (optional)
Most curtain fabric is 137 or 140 cm wide. The pattern repeat is on the label; leave 0 for plain fabric.
Each curtain, width × drop
Pole length
Drop (length)
Flat fabric width
How it hangs
Ready-made sizes to look for
Ready-made sizes are the flat width of each curtain before it's gathered. Shops in the UK sell pairs in inches; IKEA and most shops in Europe sell single panels in cm.
Fabric to make them
How it's worked out: pole or track = window width + the overlap on each side. Flat fabric width = pole length × the heading's fullness (pencil pleat and wave 2, pinch pleat 2,25, eyelet and tab top 1,5; "Fuller" adds 0,5), shared between the curtains. The drop runs from the top of the pole (eyelet, tab top), the bottom of the rings (pencil, pinch pleat and wave on a pole) or the top of the track, to 1 cm above the sill or floor, 15 cm below the sill, or 8 cm onto the floor. Fabric: each curtain gets whole or half widths of fabric after 10 cm for side hems; each drop gets 25 cm for the heading and hem, rounded up to the pattern repeat, plus one repeat to match the pattern.
Estimates only. Ready-made sizes and fabric allowances vary by shop and maker. Measure twice, with a metal tape, and check the maker's guide before you cut or order.
How it works
Pole first, then width, then drop
Curtains are sized from the pole or track, not the window. Get the pole right and everything else follows. The sources and assumptions behind it are on our How we calculate page.
Pole or track length
Window width plus 15 to 20 cm each side, so the open curtains stack clear of the glass. Measure the pole between the finials (the decorative ends), not including them.
Curtain width
Curtains are wider than the pole so they hang in folds. Pencil pleat and wave need about twice the pole length in flat fabric, pinch pleat 2.25 times, eyelet and tab top 1.5 times. For a pair, each curtain is half of that.
The drop
Measure down from the top of the pole for eyelet and tab top, or from the bottom of the rings for pencil pleat. Stop 1 cm above the sill or floor, 15 cm below the sill, or let floor-length curtains rest a few cm on the floor.
Examples
Curtain sizes for common window widths
A pair of curtains on a pole with 15 cm past the window each side, worked out with the calculator above.
Widths are the flat width of each curtain before gathering. UK ready-made widths are per curtain (46, 66, 90 or 117 inches); pick the drop separately (54, 72, 90 or 108 inches) and shorten it if needed.
Tips
Curtains that look right and keep the heat in
A few choices make a bigger difference than the fabric itself.
Go higher and wider
A pole 15 cm or more above the window and well past its sides makes the window look bigger and lets in more light. Floor-length curtains make a ceiling look taller.
Line them
Lined or thermal curtains, closed at dusk, cut the heat lost through the glass. See how much windows and walls lose with the U-Value Calculator, and keep curtains off radiators so the heat stays in the room.
Measure every window
Windows that look the same are often a few cm different, especially in older houses. Use a metal tape, measure in three places and use the widest width and the shortest drop.
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Common questions
Frequently asked questions about curtain sizes
Common questions about measuring for curtains, poles and ready-made sizes.
How do I work out what size curtains I need?
Measure the pole or track between its ends (or the window width plus 15 to 20 cm each side if you haven't got one yet). Multiply by the fullness for your heading, about 2 for pencil pleat and 1.5 for eyelet, and halve it for each curtain of a pair. Then measure the drop from the pole to where you want the curtains to end.
What size curtains for a 120 cm window?
With a 150 cm pole, each pencil pleat curtain should be about 150 cm wide flat, so a UK ready-made pair 66 inches wide. For eyelet curtains, each should be about 112 cm wide. The drop depends on the pole height and where the curtains end.
How wide should curtains be compared to the pole?
For pencil pleat and wave, the flat width of all the curtains together should be about twice the pole length; for pinch pleat 2 to 2.5 times; for eyelet and tab top about 1.5 times. Less looks flat and thin, more gives deep, heavy folds.
How far should a curtain pole extend past the window?
15 to 20 cm each side is usual. That lets the open curtains stack beside the window instead of over the glass. In a narrow alcove, use a track or a recess pole instead.
How high should a curtain pole be above the window?
About 15 cm above the top of the frame is usual, and halfway between the window and the ceiling looks good in rooms with high ceilings. Mounting the pole higher makes the window look taller.
Are ready-made curtain sizes per curtain or per pair?
In the UK the width is per curtain: a 66 × 72 inch pair is two curtains, each 66 inches wide flat and 72 inches long. Single panels sold in Europe, such as at IKEA, are sold one at a time, usually about 140 cm wide.
How much fabric do I need to make curtains?
Divide the flat width of each curtain (plus about 10 cm for side hems) by the fabric width and round up to a whole or half width. Multiply the number of widths by the drop plus 25 cm for the heading and hem, rounded up to the pattern repeat if there is one.