Sewing Calculators
Continuous bias binding.
Enter the length of binding you need and the width you cut the strips. The calculator gives the size of the square of fabric to start from, the yardage if you cut it from a flat piece instead, and an optional margin. Or enter a square you have to see how much binding it makes. Runs in your browser.
Binding length and width
Fabric needed
Fill the form and press Calculate.
Answer
For 274 in of binding cut 2 1/2 in wide, you need 685 sq in of fabric, a square about 26.2 in on each side, so start from a 27 in square. The rule is the square root of length x width.
Worked example
This matches the QUILTsocial example for a 60 x 72 in quilt: 2 x 72 + 2 x 60 + 10 = 274 in. Area = 274 x 2.5 = 685 sq in. Square root of 685 = 26.17, so a 27 in square. With a 10% margin the area is 753.5 sq in and the side 27.4 in. From a flat piece 40 in wide: 685 / 40 / 36 = 0.48 yd, so 0.5 yd. Going back, a 26 in square cut into 2.5 in bias makes about 270 in (7.5 yd) of binding before joins.
How it works
Continuous bias binding is made by cutting the square into one long spiral of bias strip, so the strip's area equals the square's area. Strip length x strip width = square area, so the side of the square is the square root of length x width. The QUILTsocial tutorial uses exactly this: multiply the binding length by the strip width, then take the square root. The extra percent is this page's own addition for squaring up edges and loss at the seams, not part of the published method. The flat-piece yardage uses the same area spread over your fabric width. Real results run a little under the ideal because of the joins, so add margin if your fabric is tight.
Sources (opened 2026-10-08): 9 steps to making continuous bias binding (QUILTsocial).
FAQ
How big a square do I need for continuous bias binding?
Multiply the binding length by the strip width and take the square root. For 274 in of 2.5 in binding that is the square root of 685, about 26.2 in, so a 27 in square.
How much binding does a 26 inch square make?
About 270 in of 2.5 in wide strip. The area (26 x 26 = 676 sq in) divided by the strip width gives the length, before allowing for joins.
How much bias binding fabric do I need from a flat piece?
Divide the area (length x strip width) by the fabric width to get the length of fabric. For 685 sq in from 40 in wide fabric that is 17.1 in, so half a yard.
Should I add extra fabric?
A small margin helps because squaring up edges and joining the strip lose a little. The extra percentage field lets you add your own; it is not from a published rule.
Why use a square?
Sewing the edges of the square together offset, as in the QUILTsocial tutorial, lets you cut one continuous strip instead of separate bands.
Disclaimer
Informational arithmetic for sewing. Real yield is slightly below the ideal because of the joins.