A visual cutting layout shows how the pieces fit.
How the fabric calculator works
Fabric is sold off a bolt by length, while its width is fixed. To know how much to buy you need to fit every piece across that width and add up the length used. FabricMath works the way most quilters and sewists cut: each kind of piece goes in its own rows, as many across as will fit, and a piece is turned sideways when that fits more in a row. The total length is converted to yards and rounded up to the next eighth of a yard, the smallest cut most shops offer, and shown in metres rounded up to the next 10 cm.
Usable width and shrinkage
Quilting cotton sold as 44 or 45 inches wide usually gives about 42 inches once the selvages are trimmed, which is why that is the default. Home décor fabric is usually 54 inches and apparel and fleece 60 inches. If you prewash cotton it can shrink by 2 to 5 percent, so the shrinkage box adds that margin to the total length.
Quilt backing
The quilt back needs to be bigger than the top so the quilter has something to hold on to; 4 inches on every side is common. If the back is wider than the fabric, panels are sewn together. The calculator works out the length for vertical seams and horizontal seams and chooses the one that uses less fabric. Extra-wide 108 inch backing often covers a whole quilt with no seams at all.
Curtains
Curtains are wider than the window so they hang in folds. Multiply the track width by the fullness, divide between the panels, add side hems and divide by the fabric width to get the number of fabric widths. Each width is cut to the finished drop plus hems. With a patterned fabric, each cut is rounded up to a whole number of pattern repeats so the panels line up. Everything is calculated in your browser.
Frequently asked questions
Why is usable width less than the label?
Selvages are trimmed off, so 44/45" cotton gives about 42" to cut from.
Should I add extra?
Add 5–10% or a few inches for straightening and mistakes.
Does it rotate pieces?
Yes, if turning a piece fits more across the width.
Is FabricMath free?
Yes, with no sign-up or ads.
Is my project saved?
Yes, in this browser only.