Quilt Backing Calculator
Work out how much backing fabric a quilt needs, and how the panels seam together. The backing has to be bigger than the top on every side, and if your fabric is narrower than the quilt you have to seam panels together, which is where most of the yardage goes.
Start from a common job
How much backing does a quilt need?
Take the quilt top and add the overage on each side. Four inches a side is the usual ask if someone else is longarming it, so check with your quilter first, because that number changes the answer more than anything else here. Then see whether your backing fabric is wide enough to cover it in one piece. Standard quilting cotton is 44 inches wide, about 42 once the selvages come off, so anything wider than that needs seaming. Wide backing at 108 inches covers most quilts in a single piece.
Worked example: backing for a throw quilt
A throw quilt, 60 by 80 inches, with 4 inches of overage on each side.
In 44 inch quilting cotton:
- The backing needs to be 68 by 88 inches: the quilt top plus 4 inches on every side.
- 44 inch fabric gives 42 usable inches, so the backing takes 2 panels with 1 seam running across the quilt.
- 2 panels is 176 inches, which is 4.89 yards, rounded up to the next quarter yard.
- Seaming the other way would take 5.75 yards.
So you buy 5 yards.
In 108 inch wide backing:
- The backing needs to be 68 by 88 inches: the quilt top plus 4 inches on every side.
- 108 inch backing covers that in one piece, with no seam.
- 88 inches is 2.44 yards, rounded up to the next quarter yard.
So you buy 2.5 yards, and there is no seam down the back.
What the backing calculator does not account for
- Shrinkage if you prewash, which quilting cotton does by a few percent.
- A directional print, which may force a seam direction and cost more than the thriftier layout above.
- The binding and the batting, which are counted separately.