Quilt Backing Calculator
Enter your quilt size to see how much fabric to buy.
How this was calculated
This is an estimate. Measure your quilt and fabric before you cut.
Allowances vary by quilter and machine. Change any value to match yours.
Free. No account. Nothing you enter leaves your browser.
Two ways to seam a backing
Panels can run with the quilt's length or across its width. The calculator works out both. The big number is the layout that takes less fabric, and the other layout sits right under it, so you can choose by seam position too.
108 inch wide backing
Wide fabric starts with a usable width of 104 inches. A smaller quilt often needs one piece and no seam. Wide backs often need more room. Ask your longarm quilter what they need.
How the amount is worked out
- Add the extra to every side of the quilt to get the backing size.
- Find how many panels cover the side they sit across, losing 1 inch to each seam.
- Multiply panels by panel length, then round up to the step you buy in.
Example: a 58 by 66 inch quilt with 4 inches per side needs a 66 by 74 inch backing. On 42-44 inch fabric, with 40 inches usable, 2 panels of 66 inches are 132 inches, so buy 3¾ yards in ¼ yard steps. Seaming the other way takes 2 panels of 74 inches, or 4¼ yards.
Presets and directional fabric
Home machine starts at 4 inches per side and Longarm at 6. If your print has a right way up, tick "My fabric has a direction" and pick the seam direction. You then see only that layout.
Questions
How much bigger should backing be than the quilt top?
We start with 4 inches on each side; many longarm quilters ask for more, so check with yours.
Do I need seams with 108 inch backing?
Often not. If your backing is wider than the usable width in both directions, it still needs a seam.
Why are there two layouts?
Seams can run along the length or across the width. They can use different amounts of fabric, so we show both.