Open Bias binding in the studio. The form on this page is that calculator.
Why bias binding is a different cut
Straight edges are happier with straight-grain binding. It is stronger, and it uses less fabric. Curves, scallops, and any corner that is not a right angle need binding cut on the bias, so the strip can stretch around the turn without puckering.
A continuous bias strip starts as a square. You cut that square from corner to corner, sew the triangles into a tube, and slice the tube into one long strip. The calculator finds the square, the yardage, and what the same quilt would take in ordinary straight-grain binding, so you can see the price of the curve before you buy.
How continuous bias binding is calculated
Add the four sides of the quilt, then add 12 inches. That extra is a little more than straight-grain binding, because the first and last inches of a bias tube are awkward to use. Multiply that length by the strip width. The square root of that area is the side of the square. It is rounded up to the next eighth of an inch, which is a size you can find on a ruler.
- Binding length = perimeter + 12 inches
- Square = square root of (length × strip width), rounded up to the next eighth
- Panels = how many widths of fabric it takes to piece that square, when the square is wider than the bolt
- Straight-grain comparison = the same quilt with 10 inches of extra, cut in ordinary strips
A 60 by 72 inch quilt with 2 1/2 inch strips needs a 26 3/8 inch square, which is 3/4 yard. The same quilt in straight-grain binding is 1/2 yard. The straight-grain binding calculator goes further into strip width and joins, and how to bind a quilt is the sewing.
Bias binding for common quilts
2 1/2 inch strips, from 42 inch usable fabric. The square is one piece at every size in this chart.
| Quilt | Bias length | Square to cut | Bias yardage | Straight-grain yardage |
|---|---|---|---|---|
| 36 × 52 in (baby) | 188 in | 21 3/4 in | 5/8 yard | 3/8 yard |
| 50 × 65 in (throw) | 242 in | 24 5/8 in | 3/4 yard | 1/2 yard |
| 60 × 72 in | 276 in | 26 3/8 in | 3/4 yard | 1/2 yard |
| 90 × 95 in (queen) | 382 in | 31 in | 7/8 yard | 3/4 yard |
How to use this calculator
- Enter the quilt width and length after it is quilted. Binding cut for the pattern's ideal size is often an inch or two short of the quilt you actually have.
- Leave the strip width at 2 1/2 inches for ordinary double-fold binding. Narrower strips make a finer edge, which can look better on a small scallop.
- Set the usable fabric width to the cloth you are cutting, usually 42 inches after the selvages.
- Press the button. The card shows the square, the yardage, and the straight-grain yardage beside it.
Tips for cutting the square
- Piece the square before you cut the diagonal if the card says the square is wider than your fabric. Sew the widths together first, then cut the square from that panel.
- Pin the bias seam. It stretches. A walking foot helps, and pressing the seam open keeps the tube flat.
- Save bias for the curves. A straight-edged quilt is stronger and cheaper in straight-grain binding. The gap on the card is the fabric the curve costs.
When the piece is part of a whole quilt. A scalloped edge still wants this square. A pieced top's own yardage is a different sum. The fabric calculator counts every piece in a design, then adds binding, backing, and batting. These pages answer one question at a time.