How much bias binding do I need for a quilt?

Add up the four sides, then add about 10 inches for the corners and the place where the ends meet. A 60 by 80 inch throw has 280 inches around, so you need about 290 inches of binding, which is 8 yards plus 2 inches.

How big a square of fabric do I need to make bias binding?

Multiply the binding length by the cut strip width, add 10 percent, and take the square root. For 290 inches of binding cut 2 inches wide, that is a square of about 25½ inches, so ¾ of a yard of fabric.

How wide do I cut bias binding?

Cut the strip four times the finished width you want to see. For the usual ½ inch double fold bias tape, cut 2 inch strips. For a ⅜ inch finish, cut 1½ inch strips, and for a ¾ inch finish cut 3 inch strips.

Do I have to use bias binding on a quilt?

No. A quilt with straight edges and square corners can be bound with strips cut on the straight grain, which is simpler and uses a little less fabric. Use bias binding for curved edges, scalloped edges, and anything that has to bend around a curve, such as a neckline or an armhole.

Bias Binding Calculator: Length and Fabric Square (Free)

Bias binding calculator

How the bias binding calculator works

Bias binding is cut on the diagonal of the fabric, at 45 degrees to the selvage (the finished edge). That direction stretches, so the binding bends around curves and corners without puckering. Straight-grain binding does not stretch, so it only suits straight edges. The calculator works out how long the binding must be, how wide to cut it, and how big a square of fabric you need to cut it as one continuous strip. Here are the steps, in order:

Cut strip width = 4 × finished widthBinding length = distance around the edge + extra for joins and cornersSquare side = √(binding length × cut strip width × 1.1), rounded up to the next ½ inFabric = square side ÷ 36, rounded up to the next ⅛ yd

The square side comes from area. A strip that is 2 in wide and 370 in long has an area of 740 square in, so you need a square of at least that area. The 1.1 adds 10 percent for the triangles lost at the ends of the strip and for the seam that joins the tube. If the square would be wider than the fabric, the calculator splits the job into two or more smaller squares, and keeps going until they fit.

Worked example. A throw quilt 60 by 80 in has 2 × (60 + 80) = 280 in around the edge. Add 10 in for corners and joins, and you need 290 in of binding. For ½ in finished binding, the strip is cut 2 in wide. The square side is √(290 × 2 × 1.1) = √638, which is a little over 25¼ in, so it rounds up to 25½ in. A 25½ in square is under 36 in on a side, so it takes just over ⅔ yd, which rounds up to ¾ yd (0.69 m).

How to cut it. Cut the square, then cut it in half along one diagonal. Put the two triangles right sides together, matching the two edges that were the straight grain, and sew them with a ¼ in seam. Press the seam open. You now have a parallelogram. Mark lines across it, parallel to the long bias edges, one strip width apart. Bring the two short edges together to make a tube, shifting one edge over by a single strip width so that the lines meet at the seam. Sew it with a ¼ in seam, then cut along the marked line, going around and around, to get one long strip. Press the strip in half lengthwise, then press both long edges in to the middle, to make double fold tape. Our quilted potholder guide shows the binding being sewn on.

Strip width for double fold bias binding

Cut strip width for each finished width
Finished width	Cut strip width	Often used for
¼ in0.6 cm	1 in2.5 cm	Tiny edges, doll clothes, narrow trim
⅜ in1 cm	1½ in3.8 cm	Baby items, lightweight fabric edges
½ in1.3 cm	2 in5.1 cm	The usual double fold bias tape, potholders, bibs, necklines
⅝ in1.6 cm	2½ in6.3 cm	Thicker layers, bags
¾ in1.9 cm	3 in7.6 cm	Quilts with thick batting, bag edges
1 in2.5 cm	4 in10.2 cm	Heavy bag edges, wide decorative binding

Quilt binding on a thick quilt is often cut a little wider, about ⅛ to ¼ in extra, to wrap the batting. Cut a test strip and check it on your own project.

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