Sewing & Fabric Calculators
Quilt Backing Fabric Calculator
This quilt backing fabric calculator tells you exactly how much backing fabric to buy. Enter your quilt top size and the calculator adds the overhang your longarmer needs, figures out how many fabric widths to seam together, and gives you the yardage rounded up to the nearest eighth of a yard.
Last reviewed: June 2026
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Your result will appear here after you press Calculate.
Yardage is rounded up to the nearest 1/8 yard and assumes you remove selvages before seaming.
Formula used
The calculator sizes the backing, then divides it into fabric widths:
- Backing width = quilt width + (2 × overhang)
- Backing length = quilt length + (2 × overhang)
- Fabric widths = round up(backing width ÷ usable fabric width)
- Total fabric = fabric widths × backing length, in the more economical orientation
- Yardage = round up(total ÷ 36) to the nearest 1/8 yard
Worked examples
Queen quilt top 60 × 80 in on 42-inch fabric
Adding 4 inches of overhang on each side gives a 68 × 88 inch backing. Two widths of 42-inch fabric are needed, so you buy about 5 yards and seam the two panels down the center.
Same quilt on 108-inch wide backing
Wide backing covers the full 68-inch width in a single piece, so you only need the length plus overhang — about 2.5 yards with no seam.
How to use this calculator
- Measure your finished quilt top width and length.
- Set the overhang your longarm quilter requests (3–4 inches per side is typical).
- Choose your fabric's usable width — about 42 inches for standard quilting cotton.
- Press Calculate to see the backing size, how many widths to seam, and the yardage to buy.
Reference chart
| Quilt size | Top (in) | Backing (in) | Approx. yardage |
|---|---|---|---|
| Baby | 36 × 48 | 44 × 56 | 3.25 yd |
| Throw | 50 × 65 | 58 × 73 | 4.25 yd |
| Twin | 70 × 90 | 78 × 98 | 5.5 yd |
| Queen | 90 × 108 | 98 × 116 | 9.75 yd |
| King | 108 × 108 | 116 × 116 | 10.25 yd |
Frequently asked questions
How much extra fabric do I need for quilt backing?
Most longarm quilters ask for 3–4 inches of extra backing on every side, so the backing is 6–8 inches wider and longer than the quilt top. This gives room to load the quilt onto the frame. The calculator adds this overhang automatically.
Do I need to piece my quilt backing?
If your backing is wider than your fabric (about 42 inches for quilting cotton), yes. The calculator tells you how many widths to seam together. Using 108-inch wide backing usually avoids seams entirely on quilts up to king size.
Should the backing seam run vertically or horizontally?
Run the seam in whichever direction uses less fabric — the calculator picks the more economical orientation for you. Many quilters prefer a horizontal seam on long quilts and a vertical seam on wide ones. Press the seam open to reduce bulk.
How much backing for a queen quilt?
A typical 90 × 108 inch queen top needs a backing around 98 × 116 inches. On 42-inch quilting cotton that's roughly 9–10 yards pieced in three widths, or about 3.5 yards of 108-inch wide backing with no seams.
Does this include batting?
No. This calculator covers backing fabric only. Batting is usually sold in the same oversized dimensions as the backing (top size plus a few inches per side), so you can use the backing size as a guide when buying batting.
Why round up to an eighth of a yard?
Fabric is cut in fractions of a yard, and a little extra protects you against cutting mistakes, shrinkage after prewashing, and squaring up the panel. Rounding up to the nearest 1/8 yard keeps you from coming up short.