How to use the quilt backing and binding calculator
- Enter the width and length of the finished quilt top in inches.
- Enter the extra backing you want on each side, the usable width of your fabric after trimming the selvages, and the cut width of your binding strips.
- Open the advanced option to change the extra length of binding allowed for corners and joins.
- Read the backing size, the layout that uses the least fabric, the yards to buy, the number of binding strips and the minimum batting size.
Formula
Backing size = quilt size + 2 x extra on each side
Seams the long way: panels = ceil(backing width / fabric width), yards = panels x backing length / 36
Seams across: panels = ceil(backing length / fabric width), yards = panels x backing width / 36
Binding length = 2 x (width + length) + extra; strips = ceil(binding length / fabric width); yards = strips x strip width / 36
The smaller of the two backing layouts is used, and both backing and binding are rounded up to the next eighth of a yard, which is how fabric is usually cut in the shop.
Worked example
A quilt top is 60 by 72 inches. With 4 inches extra on every side the backing is 68 by 80 inches. With 42 inch fabric, seams running the long way need 2 panels of 80 inches, or 4.44 yards. Seams across need 2 panels of 68 inches, which is 3.78 yards. The second layout wins, so you buy 3.875 yards.
The binding runs 2 x (60 + 72) = 264 inches plus 12 inches for corners and joins, so 276 inches. At 42 inches per strip that is 7 strips of 2.5 inches, which is 0.49 yards, so buy 0.5 yard.
If you use 108 inch wide backing instead, one panel is enough, and the yardage falls to 1.89, so you buy 2 yards.
Why extra backing matters
The backing and batting are made larger than the top so that the layers can shift while you quilt, especially on a long arm machine, where the edges are clamped. Four inches on each side is a common allowance, and some quilters want six. Trim the extra off after quilting and before the binding goes on.
Batting is cut to the same size as the backing, so the size in the results is the least you need. Packaged batting comes in set sizes, so choose the one that is at least that large in both directions.
Binding notes
Binding is a strip folded over the raw edge. How much you need depends on the width of the strips and the way you join them.
- Strips are cut across the width of the fabric and joined end to end, usually with a diagonal seam that loses a little length.
- The 12 inches allowed for corners and joins is a common rule. Add more if you want a wider binding or a wavy edge.
- A strip cut 2.5 inches wide and folded in half gives a binding of about a quarter inch on the front for a standard quilt.
- Prewash and shrinkage can change the usable width. Buy a little extra if you wash fabric first.
Assumptions and limits
- The fabric width is the usable width after trimming selvages, commonly about 40 to 42 inches for quilting cotton.
- Backing is cut from plain fabric with no pattern to match. Directional prints and matching seams need extra yardage.
- Yardage is rounded up to the next eighth of a yard.
- The batting size is the same as the backing size and is a minimum.
Frequently asked questions
How much backing fabric do I need for a quilt?
Add 8 inches to the quilt's width and length, then work out how many fabric widths you need and multiply by the length. This calculator tries both layouts and gives the one that needs the least fabric.
How much binding do I need for a 60 by 72 inch quilt?
The edge is 264 inches around. With 12 inches extra for corners and joins and 42 inch strips, you need 7 strips of 2.5 inches, so half a yard is enough.
Should the backing seam run lengthwise or crosswise?
Either works. Many quilters choose the layout that uses less fabric, and some prefer a seam that runs the same way as the quilting. The result shows the direction of the seam for the cheaper layout.
What size batting should I buy?
Batting should be at least as large as the backing. For a 60 by 72 inch top with 4 inches extra, you need at least 68 by 80 inches, so a twin or a full size package is common.