Quilt backing, binding and batting calculator
Enter the size of your finished quilt top. You get the backing yardage, pieced whichever way uses less fabric, the number of binding strips and the fabric for them, and the batting size to buy.
Backing
3 7/8 yd
Backing must be 68" × 80". Least fabric: 2 panels of 68", 1 horizontal seam. The other way round would be 2 panels of 80", 1 vertical seam, 4 1/2 yd.
Binding
1/2 yd
7 strips of 2.5" cut across 42" fabric, for 276" of binding (264" perimeter plus 12").
Batting
68" × 80"
The smallest typical packaged size that covers it is Twin (72" × 90"); check the package, brands vary.
How each number is worked out
Backing
The backing has to be the quilt top plus the overage on every side:
top width + 2 × overage by top length + 2 × overage. When that is wider
than the fabric, panels are sewn together. Each seam uses the seam allowance (1/2" for a 1/4" seam,
which takes 1/4" from each panel), so n panels cover
n × fabric width − (n − 1) × seam.
There are two ways to piece it. Vertical seams: panels run the length of the quilt, side by side, each as long as the backing. Horizontal seams: panels run across the quilt, stacked, each as long as the backing is wide. The calculator works out both and recommends the one that needs less fabric, then rounds up to the next 1/8 yard.
Binding
binding length = 2 × (width + length) + extra, using the quilt top's finished size.
Strips are cut selvedge to selvedge and joined with diagonal seams. Each diagonal join uses roughly one
strip width of length, so each strip is counted as giving fabric width − strip width.
Then strips = ceil(binding length / usable length per strip) and the fabric needed is
strips × strip width, rounded up to the next 1/8 yard.
Batting
The same size as the backing. The calculator suggests the smallest of the usual packaged sizes that covers it, in either orientation.
Worked example
A 60 × 72" throw, with 4" of overage per side and 42" usable backing fabric: the backing must be 68 × 80".
- Vertical seams: 68" of width needs two panels (2 × 42 − 1/2 = 83 1/2" of cover), each 80" long, so 160", or 4 1/2 yards once rounded.
- Horizontal seams: 80" of length also needs two panels, but each is only 68" long, so 136" or 3.78 yards: buy 3 7/8 yards. That is five-eighths of a yard less for the same backing.
- Binding: 2 × (60 + 72) + 12 = 276". Each 2 1/2" strip gives 42 − 2.5 = 39.5", so 276 / 39.5 = 6.99, which is 7 strips, 17 1/2" of fabric: 1/2 yard.
- Batting: 68 × 80", which a typical twin-size package (72 × 90") covers.
Backing and binding for example sizes
With 4" overage per side, 1/2" seams, 42" usable cotton for backing and binding, and 2 1/2" strips. The wide-backing column assumes 106" usable width.
| Quilt top | Backing (42") | Panels | Wide backing | Binding |
|---|---|---|---|---|
| 36 × 52" | 2 1/2 yd | 2 | 1 1/4 yd | 3/8 yd |
| 50 × 65" | 3 1/4 yd | 2 | 1 5/8 yd | 1/2 yd |
| 60 × 72" | 3 7/8 yd | 2 | 2 yd | 1/2 yd |
| 72 × 90" | 5 1/2 yd | 2 | 2 1/4 yd | 5/8 yd |
| 90 × 108" | 8 1/4 yd | 3 | 3 1/4 yd | 7/8 yd |
| 108 × 108" | 9 3/4 yd | 3 | 6 1/2 yd | 7/8 yd |
Where it stops being reliable
- It assumes whole panels. When a backing is only a little wider than one width of fabric, a narrow strip pieced from leftovers can replace the whole second panel and save a lot of yardage. The calculator does not suggest that; look out for it when one direction needs just over a whole number of panels.
- Directional prints on the back may force a seam direction that is not the cheapest.
- Bias binding, for curved or scalloped edges, is cut differently and needs its own calculation.
- Shrinkage is not included. If you pre-wash, add a few percent, or use the fabric yardage calculator, which has a shrinkage setting.
Common questions
How much bigger than the quilt top should the backing be?
Longarm quilters commonly ask for about 4 inches extra on every side, 8 inches in total in each direction, because the machine frame needs something to hold and the quilting draws the layers in. For quilting on a domestic machine, 2 to 3 inches per side is often enough. If someone else is quilting it, ask them: their requirement overrides any rule of thumb.
Should backing seams run vertically or horizontally?
Whichever uses less fabric, unless your quilter has a preference. Many longarm quilters prefer seams running parallel to the rollers, which is horizontal as the quilt is usually loaded, but ask. The calculator shows both directions and which is cheaper.
How wide should binding strips be?
A double-fold binding cut 2 1/2 inches wide is the most common choice; sewn with a 1/4-inch seam it shows roughly 3/8 to 1/2 inch on the front, depending on the batting thickness. 2 1/4 inches gives a narrower, snugger binding; 2 3/4 or 3 inches suits thick batting or a wider look. Change the strip width and the yardage follows.
Why add extra length to the binding?
Mitring four corners and joining the two ends takes length, and you need a tail at the start. About 10 to 12 inches over the perimeter is the usual allowance; the default here is 12.
Can I use wide backing fabric?
Yes. Wide backings are sold around 108 inches wide. Set the backing width to its usable width, about 104 to 106 inches, and most quilts up to queen size need a single seamless length. The table below shows how much that saves.
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