What this calculator does
Binding is the narrow strip that wraps the raw edge of a quilt. It looks like a small job, but it is the one cut where running out is painful: the fabric is often from a collection that is no longer in the shop by the time you finish quilting. This calculator works out exactly how many strips you need, so you can buy the binding with the rest of the fabric.
It assumes you cut straight-grain strips across the width of the fabric (selvage to selvage), join them end to end with diagonal seams, then fold the long strip in half for a double-fold binding. That is how most modern quilt patterns finish a quilt.
How to use it
- Measure the finished, quilted size. Quilting shrinks the top a little, so measure after quilting if you can.
- Enter width and length in inches.
- Pick your strip width. If your pattern says "cut 7 strips 2½″ × WOF", that 2½″ is the strip width.
- Cut the number of strips shown. The result also shows how much will be left over after joining.
The math
binding length = 2 × (width + length) + 10″
strips = round up (binding length ÷ usable width)
fabric = strips × strip width, rounded up to 1/8 yd
For a 60 × 72 inch throw, the perimeter is 2 × (60 + 72) = 264 inches. Add 10 and you need 274 inches of binding. Divided by 42 that is 6.5, so you cut 7 strips. At 2½ inches each, that is 17.5 inches of fabric, which rounds up to 1/2 yd.
Binding for common quilt sizes
2½ inch strips on 42 inch usable fabric.
| Quilt | Size | Strips | Fabric |
|---|---|---|---|
| Baby | 36 × 52″ | 5 | 3/8 yd |
| Lap / throw | 50 × 65″ | 6 | 1/2 yd |
| Twin | 70 × 90″ | 8 | 5/8 yd |
| Full | 85 × 108″ | 10 | 3/4 yd |
| Queen | 90 × 108″ | 10 | 3/4 yd |
| King | 108 × 108″ | 11 | 7/8 yd |
Tips
Buy a little extra. If you have never cut binding before, or your ruler slips, one spare strip is cheap insurance. An extra 1/8 yard gives you one more 2½ inch strip with room to straighten the edge.
Press before you sew. Press the long joined strip in half lengthwise, wrong sides together, before you sew it on. A crisp fold makes the hand-stitched or machine-stitched back look even.
Planning the whole quilt at once? The backing calculator and batting calculator use the same quilt size.
Questions people ask
What width should I cut binding strips?
2½ inches is the most common width for double-fold binding on a quilt with regular cotton batting. 2¼ inches gives a narrower, snugger edge. Thick or wool batting usually needs 2¾ inches. Whatever you choose, the calculator multiplies the strip count by that width.
Why add 10 inches to the perimeter?
Each mitered corner uses a little extra, and you need a tail at the start and end to join the binding neatly. 10 inches covers that for most quilts. Many quilters add 12 to 20 inches to be safe, and the leftover from the last strip usually gives you that cushion anyway.
Do I need bias binding?
Only for curved or scalloped edges. Straight-grain strips cut across the width of fabric are fine for straight-edged quilts and use less fabric. Bias binding needs more yardage because the strips are cut on the diagonal.
How do I join binding strips?
Lay two strips right sides together at a right angle, sew from corner to corner on the diagonal, trim to a quarter inch and press open. Diagonal joins spread the bulk so the binding lies flat.
Can I use leftover backing for binding?
Yes, as long as the strips are long enough. Strips cut along the length of a long backing piece can be longer than 42 inches, which means fewer joins. Use the total binding length in the result to check.