Quilt Backing Calculator
Backing has to be bigger than the top, and how you orient the panels decides how much you buy. Enter your quilt size, overhang, and fabric width to get the yardage, panel count, and seam layout — including whether wide backing saves you a seam.
Three to four inches is typical; longarm quilters often ask for four or more.
Formula & how it works
Backing size is quilt + overhang × 2 in each direction. Usable fabric width deducts about an inch of selvedge, and each joining seam consumes seam allowance × 2.
Both orientations are tested — panels running along the length, or rotated — and the one needing less fabric is reported: panels × the other dimension.
Worked example
A 60 × 80 inch quilt with 4 inches of overhang needs a backing of 68 × 88 inches. On 44-inch fabric that takes two panels 88 inches long — about 4.9 yards with one seam. Switch to 108-inch wide backing and a single 68-inch length does it: under 2 yards, no seam.
Planning the back
Why the overhang matters
The backing must be larger than the top because quilting draws the layers in and any shift during basting or longarm loading eats the margin. Three to four inches per side is the norm, and if you are sending the quilt out, ask your quilter what they require before cutting.
Orientation changes the yardage
Running seams one way versus the other can change the fabric needed substantially. A backing slightly narrower than two fabric widths in one direction might fit within a single width when rotated, which is why comparing both is worth the moment it takes.
Wide backing earns its price
Fabric sold at 108 inches costs more per yard but frequently needs fewer yards and no piecing at all. For anything from a throw upward it often works out cheaper overall, and it removes a bulky seam that can show through the quilting.