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YardageLab

Quilt Backing Calculator

Work out how much backing fabric to buy, how many panels to cut and which way the seam should run.

Units
in
in
Fabric width (usable)
in

Usable width between selvedges — often 42″ for quilting cotton, 108″ for wide backing.

in

Extra on each edge (4″ is typical for long-arm).

in

Backing fabric to buy

5yd

≈ 180 in off the bolt

Exact math

4.92 yd

Buy (rounded up)

5 yd

Backing width
68 in
Backing length
88 in
Panels
2
Seam
Vertical
Each panel
42 in
Cut length
88.5 in
2 panels with vertical seam
Assumptions used
Overhang per side
4 in
Usable fabric width
42 in
Seam allowance
0.25 in per join
Directional print
no
Purchase rounded up to
0.25 yd

Methodology

How the backing calculation works

Your quilt back needs to be larger than the quilt top so it can be loaded onto a frame and survive the take-up of quilting. We add your overhang to every side:

  • Backing width = quilt width + (2 × overhang)
  • Backing length = quilt length + (2 × overhang)

Because quilting cotton comes in a fixed usable width (often about 42″), a normal-sized quilt back is pieced from full-width panels seamed together. We test both seam directions — panels running the length of the quilt, or rotated to run across it — and keep whichever uses the least fabric. Directional prints skip the rotation option so your pattern always runs the right way.

Each panel’s cut length includes a seam allowance at every join. We then convert the total length pulled off the bolt into yards and round up to the next quarter yard, so you never come up short at the cutting counter.

See it in numbers

Worked example

A 60″ × 80″ quilt with a 4″ overhang on 42″ fabric:

  • Backing needed: 68″ × 88″
  • 68″ ÷ 42″ = 1.62 → 2 panels, seams running vertically
  • Each panel cut 88″ + seam allowance ≈ 88.5″; two panels ≈ 177″
  • 177″ ÷ 36 = 4.92 yd exact → buy 5 yd

Reference

Common fabric widths & overhangs

FabricUsable widthBest for
Quilting cotton42–44 inMost quilts (pieced back)
Wide backing108 inSeamless backs up to king
Extra-wide muslin90–120 inUtility & practice quilts

Overhang guidance: hand or domestic machine quilting needs about 2–3″ per side; long-arm quilters usually ask for 4″ per side. When in doubt, ask your quilter first.

Frequently asked questions

Should I buy extra beyond the recommendation?
The recommended amount already rounds up and includes overhang and seam allowance. If your cutter is generous with straightening or you want insurance against a crooked cut, add another quarter yard.
Why did the seam direction change when I resized the quilt?
We always pick the orientation that uses less fabric. As the quilt’s proportions change, the cheaper direction can flip between vertical and horizontal seams.
What if I use 108″ wide backing?
Enter 108 as the fabric width. For most quilts one width will cover the whole back with no seam, and the tool will tell you so.
Does this include batting?
No — this calculates the backing fabric only. Batting is usually cut to the same size as the backing.

Transparency

Sources & assumptions

  • Panels are cut the full usable width of the fabric and seamed side by side.
  • Default usable width 42″; adjust to match your specific fabric.
  • Seam allowance is added to each panel join; the default is ¼″.
  • Purchase yardage is rounded up to the next ¼ yard.
  • This tool gives fabric estimates for planning — always confirm against your quilter’s requirements before buying.

Keep planning

Related calculators

Quilt Binding CalculatorFind the binding length, number of strips and fabric you need to bind the edge of your quilt.Quilt Size CalculatorTurn a block size and layout into finished quilt dimensions and the closest standard bed size.Fabric Unit ConverterConvert between inches, feet, yards, millimeters, centimeters and meters for fabric and cutting.

Last reviewed August 23, 2026

Found an error? Tell us — every formula is human-reviewed.