Curtain & Drapery Fabric Calculator
Calculate the fabric yardage for curtains from the rod or window width, finished drop, heading style or fullness, single panel or pair, bolt width, hems, returns, overlap and pattern repeat — with half widths, railroading, lining, several windows and the cost.
How it works
Rod width = window width + 2 × rod extension · Flat width = (rod width + returns + overlap) × fullness + side hems · Widths per curtain = flat width ÷ curtains ÷ fabric width, rounded up to a whole (or half) width · Cut length = drop + hem and heading allowance, rounded up to whole pattern repeats · Fabric = cuts × cut length × windows (+ one repeat for placement) ÷ 36, rounded up to the next ¼ yard · Railroaded: fabric = flat width ÷ 36 · Cost = yards × price
Curtains look full because they use far more fabric than the window is wide — a fullness ratio of two to two-and-a-half times is what gives gathered drapes their body, and each heading style has its usual ratio: about 2.5× for pinch pleats, pencil pleats and rod pockets, 2× for grommets and wave headings, 1.5× for flat panels and up to 3× for sheers. Start from the rod width (or the window plus the rod extension on each side), add any returns and centre overlap, multiply by the fullness and add the side hems. Dividing by the fabric width gives the number of widths; for a pair, one width can be split so each curtain gets a half, which often saves a whole cut. Each cut is the finished drop plus the hem and heading allowance, rounded up to whole pattern repeats so the print matches across seams. Multiply cuts by cut length, convert to yards and round up to the next quarter yard. Extra-wide fabric can be railroaded — turned sideways so the bolt width becomes the curtain length — which needs only the flat width in yardage and no seams. Lining is worked out the same way without pattern matching.
Worked example
A 60 in rod at 2× fullness for a pair needs 120 in of flat fabric, or 60 in per curtain. On a 54 in bolt that is 60 ÷ 54 = 1.11 → 1½ widths per curtain, 3 widths in total, cut from 3 drops. Each cut is the 84 in drop plus 16 in of hems = 100 in. Three cuts total 300 in = 8.33 yards, rounded up to 8.5 yards, or $127.50 at $15 a yard. With a 24 in pattern repeat each cut grows to 5 × 24 = 120 in, so the same curtains need 360 in = 10 yards. Choosing pinch pleats (2.5×) instead gives 75 in per curtain → 1½ widths each, still 3 cuts.
Frequently asked questions
How much fabric do I need for curtains?
Multiply the rod width by your fullness ratio and divide by the fabric width to get the number of widths, then multiply by each drop’s cut length (finished length plus hems, rounded up to whole pattern repeats) and convert to yards. Round up generously — running short mid-project is costly.
What fullness ratio should I use?
About 2× the track width gives a standard gathered look, 2.5× to 3× makes luxurious pleated drapes, and 1.5× suits flat, modern panels. Pick a heading style and the calculator uses its usual ratio: 2.5× for pinch pleat, pencil pleat and rod pocket, 2× for grommet and wave, 1.75× for tab top and 3× for sheers.
Why does a patterned fabric need more?
To make the print match across panels, every cut must begin at the same point in the repeat, so each length is rounded up to a whole number of repeats. A large repeat can add substantial extra yardage compared with a plain fabric — the calculator shows how much.
What are half widths?
When a pair needs, say, 1½ widths per curtain, you can cut one width lengthways and give each curtain half. That makes 3 cuts instead of 4. Sew the half at the outer edge of each curtain so the seam hides in the folds.
Should I measure the window or the rod?
Measure the rod or track if it is already up. If not, measure the window opening and add how far the rod will extend on each side — usually 4–10 in — so open curtains stack clear of the glass. Choose “Window opening” and the calculator adds the extension for you.
What does railroading fabric mean?
Turning the fabric sideways so its width runs from top to bottom. It only works when the bolt is wider than the cut length — common with 110–118 in sheers — and it removes seams entirely: you buy just the flat width in yards.
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This calculator is for educational purposes. Double-check important results before acting on them.