Quilt Backing Calculator
Enter the size of your quilt top and the width of your backing fabric. The calculator adds extra on every side, tries both seam directions, and tells you how much to buy.
By QuiltFigureUpdated 1 source cited
Longarm quilters usually ask for 4 in; check with yours.
Backing fabric to buy
5 yd
How the backing calculation works
First the calculator adds the extra you need on each side. Longarm quilters usually ask for about 4 inches all round, so a 60 × 80 inch top needs a 68 × 88 inch backing.
Quilting cotton is only about 42 inches wide once the selvages are trimmed, so most backings are pieced from two or three panels. Each seam is sewn with a 1/2 inch seam allowance, which uses 1 inch of width per seam. Two 42 inch panels therefore cover 83 inches, not 84.
Panels can run the length of the quilt (vertical seams) or across it (horizontal seams). The calculator works out both and recommends the one that uses less fabric, then rounds up to the next 1/8 yard because that is how fabric shops cut.
Worked example
For a 60 × 80 inch quilt with 4 inches extra per side on 42 inch fabric, two panels cut 88 inches long cover the 68 inch width: 176 inches, or 5 yards. Running the seams across would take three 68 inch panels, 204 inches, so the vertical layout saves almost a yard.
How to piece a quilt backing
Once the calculator has told you how many panels to cut, piecing the backing takes about half an hour.
- Prewash the backing if you prewashed the top, then trim off both selvages.
- Cut the number of panels shown, each to the cut length shown.
- Sew the panels together along their long edges with a 1/2 inch seam.
- Press the seams open so they lie flat under the quilting.
- Check the backing is at least the backing size shown, then square it up before layering.
108-inch wide quilt backing
Wide backing fabric for quilts is 108 inches wide (some is 104 to 120 inches), so most quilts up to king size need just one piece and no seams. It costs more per yard but often less in total, and there is no seam to quilt over. Choose the 108 inch option in the calculator to compare.
Not sure of your finished size yet? Start with the quilt size chart. Need the edge too? Use the quilt binding calculator.
Common questions
How much bigger should quilt backing be than the quilt top?
Most longarm quilters ask for 4 inches extra on every side, so 8 inches more in width and in length. If you quilt on a domestic machine, 2 to 3 inches per side is usually enough.
How much backing do I need for a queen quilt?
For an 84 × 102 inch queen quilt with 4 inches extra per side on 42 inch fabric, you need three panels of 92 inches, about 7 3/4 yards. In 108 inch wide backing it is one 110 inch piece, so buy 3 1/8 yards.
Should backing seams run vertically or horizontally?
Either works. Pick the direction that uses less fabric, which the calculator shows. Some longarm quilters prefer horizontal seams because they roll more evenly on the frame, so ask yours.
Why round up to the nearest 1/8 yard?
Fabric shops cut in eighths of a yard, and fabric is rarely cut perfectly straight. Rounding up makes sure you are never short.
Sources
- 1.Backing and Batting Calculator — Quilter's Paradise — 1 inch per seam, both seam directions compared, yardage rounded up to 1/8 yard
