How to use the curtain fabric calculator
- Enter the width to cover (the rod or window) and the fullness you want, such as 2 for twice the width.
- Enter the fabric width, the finished length and the allowances for the bottom hem, top header and side hems.
- Choose one panel or a pair, add a pattern repeat if the fabric is printed, and an extra percent.
- Read the number of widths, the cut length and the yards to buy.
Formula
Finished width = width to cover x fullness
Flat width = finished width + side hems (2 per panel)
Widths = flat width / fabric width, rounded up (and to an even number for a pair)
Cut length = finished length + hem + header, rounded up to a whole pattern repeat
Yards = widths x cut length x (1 + extra) / 36, rounded up to the next eighth
A yard is 36 inches. The final figure is rounded up to the next eighth of a yard so you do not come up short.
A 60 inch window at twice the width
A 60 inch window at 2x fullness needs 120 inches of finished width, or 123 inches with 1.5 inch side hems on both edges of one panel. On 44 inch fabric that is 2.8 widths, so 3 widths are needed. With an 84 inch curtain, 8 inches of hem and a 4 inch header, each width is cut 96 inches long.
That is 3 x 96 = 288 inches. With 5% extra, 302.4 inches is 8.4 yards, so buy 8.5 yards. For a pair, the widths must be even, so 4 widths are cut. With no extra that is 10.667 yards, which is 10.75 yards to buy. A 27 inch pattern repeat rounds each cut up to 108 inches.
Fullness and widths
Fullness is how much extra fabric makes the folds when the curtain is closed. Twice the width is a starting point many sewists choose, and heavier fabrics or a more gathered look may call for more, so it is an input. Each width of fabric is one length cut from the roll, and curtains use whole widths joined at the selvage, which is why the count rounds up.
For other fabric projects, use the fabric yardage calculator and the quilt backing and binding calculator.
Patterns and lining
A printed fabric has a repeat, and the pattern has to line up across widths, so every cut length is rounded up to a whole repeat. This tool handles a straight repeat. Fabrics with a half drop repeat need more, so ask the seller.
Lining, interlining, trim and pleat spacing are not included. Measure the window and the wall space with the rug size calculator for nearby furnishing, or plan the wall with the wallpaper calculator.
Assumptions and limits
- Fullness, hems, header and extra percent are example values that depend on your style and fabric.
- Fabric width is the usable width between the selvages after allowing for any shrinkage you expect.
- A straight pattern repeat is assumed.
- Lining, trim and pleats are not included.
Frequently asked questions
How much fabric do I need for curtains?
Multiply the rod width by the fullness, divide by the fabric width and round up to find the widths. Multiply by the cut length and divide by 36 for yards.
What is curtain fullness?
It is the ratio of the fabric width to the width of the space. Two means the fabric is twice as wide as the rod.
Why do pairs need an even number of widths?
Each panel of a pair has to have the same number of widths so the two sides match, so an odd count is raised to the next even number.
How do I account for a pattern repeat?
Enter the repeat length. The tool rounds each cut length up to a whole repeat so the pattern lines up across widths.