Free sewing & quilting calculators
Curtain Fabric Calculator
How much fabric to buy for curtains — from your rod width, the drop, and how full you want them to hang. Pattern repeats included.
How curtain yardage is calculated
Curtains are deliberately wider than their window — that's what makes the folds. The fullness ratio is how many rod widths of flat fabric go into the gathers: a 72 in rod at 2× fullness needs 144 in of flat fabric across it, split between however many panels you're making.
Each panel then needs side hems, and it has to be built from whole widths of fabric. A 72 in flat panel plus 4 in of side hems is 76 in wide, and 54 in home-décor fabric gives about 52 in usable — so that panel takes two widths seamed together, and a pair of curtains takes four cuts in total.
Finally each cut is made long enough for the drop plus its hems. Curtains want deep hems: 8 in at the bottom (folded double, so it hangs with weight) and 8 in at the top for the heading or rod pocket is a common allowance, which is the 16 in default above. Multiply the number of cuts by the cut length, divide by 36, and that's your yardage.
yards = widths × (drop + hems) ÷ 36, where widths = ⌈(rod × fullness ÷ panels + side hems) ÷ usable fabric width⌉ × panels.
How full is full?
| 1.5× | Flat and tailored. Fine for stationary side panels that never close, or heavy fabric where more would be bulky. |
|---|---|
| 2× | The standard. Reads as a proper curtain, closes over the window, suits most rod-pocket and grommet headings. |
| 2.5× | Full and luxurious — what pinch-pleat and goblet headings expect, and what makes a room look finished. |
| 3× | Sheers and voiles. Lightweight fabric needs more of it before the gathers read as anything at all. |
Fullness is the setting people get wrong, and always in the same direction. Ready-made curtains are usually sold at around 1.5× because fabric is the cost, which is exactly why home-made curtains at 2.5× look so much better than shop ones. If you're between two numbers, go up.
Measuring the drop
Measure from the rod, not from the window. Hang the rod first — 4–6 in above the window frame and 6–10 in wider on each side is the usual advice, because it makes the window look larger and lets the curtains stack off the glass — then measure from where the fabric will actually hang to where you want it to stop. Measure the rod width the same way: the calculator wants the width of the rod you've hung, not the window it covers.
For the bottom, pick a look: sill length stops ½ in above the sill, apron length falls 4 in below the frame, floor length stops ½ in off the floor, and a puddle adds 2–6 in that pools on purpose. Then measure the drop three times — at the left, middle, and right of the window — and use the longest. Floors and ceilings are rarely as level as they look, and a curtain cut to the short measurement will hang visibly crooked.
Pattern repeats
A printed or woven fabric has a repeat: the distance before the design starts again. Every cut has to begin at the same point in that design, or the panels won't match each other where they meet. That means each cut gets rounded up to a whole number of repeats, and the remainder is waste you still pay for.
It adds up fast. A 100 in cut from fabric with a 24 in repeat becomes 120 in — five repeats — so four cuts waste 80 in, over two yards, before you've sewn anything. Enter the repeat above and it's counted for you. The repeat is printed on the fabric bolt or listed in the online description; if you can't find it, measure between two identical points in the design.
Buy it all at once
Whatever the total comes to, buy it in one go, from one bolt. Dye lots vary more than you'd expect, and a curtain panel that's a shade off from its partner is obvious in daylight in a way it never is in the shop. The suggested-buy figure adds 5% for shrinkage on top — worth having if you plan to wash the curtains, and cheap insurance if you don't.