Enter the length and width of the quilt top in inches, the usable width of the backing fabric and the width of your binding strips, commonly 2.25 to 2.5 inches. Use the quilter’s requested backing allowance. With an assumed 4 inches on each side, an 80-by-60-inch top needs an 88-by-68-inch backing before seam and fabric-width planning.
If the backing plus overhang is wider than the fabric, two widths are pieced together. Binding is cut in strips joined end to end.
The calculation reserves one inch of width per backing join for two half-inch seam allowances. It assumes the selected four-inch margin, not every quilter’s requirement. Confirm the longarm provider’s margin, washing shrinkage, directional layout and usable selvage-free width.
Backing fabric needed (yards) from quilt top length
| Quilt top length | 80 |
|---|---|
| Quilt top width | 60 |
| Backing/binding fabric width | 42 |
| Binding strip width | 2.5 |
| Backing fabric needed (yards) | 4.9 |
| Binding fabric needed (yards) | 0.556 |
Common error: Cutting the backing to the size of the top. Quilting shrinks the top slightly and needs the extra fabric, and a backing that is too small leaves the edges bare.
Quilt Backing & Binding: formula
Quilt Backing & Binding: changing Quilt top length
| Quilt top length | Backing fabric needed (yards) | Binding fabric needed (yards) |
|---|---|---|
| 64 | 4 | 0.486 |
| 72 | 4.4 | 0.556 |
| 80 (example) | 4.9 | 0.556 |
| 88 | 5.3 | 0.625 |
| 96 | 5.8 | 0.625 |
Quilt Backing & Binding: compare input ranges
| Input | Tested from | To | Backing fabric needed (yards): low input | Backing fabric needed (yards): high input | Swing |
|---|---|---|---|---|---|
| Quilt top length | 72 | 88 | 4.4 | 5.3 | 0.889 (18%) |
| Quilt top width | 54 | 66 | 4.9 | 4.9 | 0 |
| Backing/binding fabric width | 38 | 46 | 4.9 | 4.9 | 0 |
| Binding strip width | 2.3 | 2.8 | 4.9 | 4.9 | 0 |
Quilt Backing & Binding: individual input comparisons
| Input | Value | Backing fabric needed (yards) | Binding fabric needed (yards) |
|---|---|---|---|
| Quilt top length | 64 | 4 | 0.486 |
| 72 | 4.4 | 0.556 | |
| 80 | 4.9 | 0.556 | |
| 88 | 5.3 | 0.625 | |
| 96 | 5.8 | 0.625 | |
| Quilt top width | 48 | 4.9 | 0.556 |
| 54 | 4.9 | 0.556 | |
| 60 | 4.9 | 0.556 | |
| 66 | 4.9 | 0.625 | |
| 72 | 4.9 | 0.625 | |
| Backing/binding fabric width | 34 | 7.3 | 0.694 |
| 38 | 4.9 | 0.625 | |
| 42 | 4.9 | 0.556 | |
| 46 | 4.9 | 0.486 | |
| 50 | 4.9 | 0.486 | |
| Binding strip width | 2 | 4.9 | 0.444 |
| 2.3 | 4.9 | 0.5 | |
| 2.5 | 4.9 | 0.556 | |
| 2.8 | 4.9 | 0.611 | |
| 3 | 4.9 | 0.667 |
Backing fabric needed (yards): Quilt top length against Quilt top width
| Quilt top length / Quilt top width | 48 | 60 | 72 |
|---|---|---|---|
| 64 | 4 | 4 | 4 |
| 72 | 4.4 | 4.4 | 4.4 |
| 80 | 4.9 | 4.9 | 4.9 |
| 88 | 5.3 | 5.3 | 5.3 |
| 96 | 5.8 | 5.8 | 5.8 |
Quilt Backing & Binding: values and definitions
| Quantity and definition | Value used |
|---|---|
| Quilt top length — Finished quilt top length, in inches. | 80 |
| Quilt top width — Finished quilt top width, in inches. | 60 |
| Backing/binding fabric width — Usable width of your backing and binding fabric, in inches. | 42 |
| Binding strip width — Cut width of each binding strip, in inches. | 2.5 |
| Backing fabric needed (yards) | 4.9 |
| Binding fabric needed (yards) | 0.556 |
Quilt top length: half and double
| Quilt top length | Backing fabric needed (yards) |
|---|---|
| 40 | 2.7 |
| 80 | 4.9 |
| 160 | 9.3 |
A quilt's backing must be larger than the top, and when the top is wider than the fabric the backing needs a seam. An 80 by 60 inch top on 42 inch fabric needs two widths joined, which takes about 4.9 yards. Binding is the perimeter times a small allowance divided into strips of a set width, and 2.5 inch strips need about 0.556 yards.
Quilting draws the layers in, so the backing needs a few inches extra on every side.
Add several inches of overhang on each side of the backing, and decide the seam direction so the seam is not in the center of the quilt if you want it hidden.
See fabric estimates on the fabric yardage calculator, seam allowances on the seam allowance page and scaling on the pattern scaling calculator. The rectangle area and perimeter calculators give the measurements, and the unit conversion pages convert inches and centimeters.
Does this calculate bias binding?
No. The example uses straight strips; a bias layout needs its own cutting plan.