Tool
Quilt backing & binding calculator
Pick a standard size or type your own. The backing is worked out both ways, seams running down the quilt or across it, and the cheaper one is shown first. Free, no account, nothing saved.
What to buy
Backing
1¾ yd
one piece, no seam
Binding
½ yd
5 strips × 2.5 in
Batting, cut to
44 × 56 in
same as the backing
Show the math
- Cut size. 36 + 2 × 4 = 44 in wide, 48 + 2 × 4 = 56 in long. Backing and batting are both cut to this, then trimmed flush after quilting.
- Backing, vertical seams (none needed). 44 in fits in 44 in, so 1 length. 1 × 56 in = 56 in = 1.56 yd, rounded up to 1¾ yd.
- The other layout, horizontal seams. 2 lengths × 44 in − 1 seam × 1 in = 87 in, enough to span 56 in down the length. 2 × 44 in = 88 in = 2.44 yd, rounded up to 2½ yd. That is ¾ yd more.
- Binding length. 2 × (36 + 48) = 168 in around the edge, + 10 in for the starting tail, the closing join and the mitred corners = 178 in.
- Binding strips. Cut 2.5 in strips across the 40 in usable width. Each diagonal join uses about one strip width, so 5 strips give 5 × 40 − 4 × 2.5 = 190 in, which covers 178 in. Fabric: 5 × 2.5 = 12.5 in = 0.35 yd, rounded up to ½ yd.
Rounded up to the next quarter yard, the way most shops cut. If you prewash, measure the usable width afterwards: Moda puts quilting cotton shrinkage at 3 to 5 percent, mostly across the width, so a backing that only just fits can come up short (should you prewash fabric?).
Standard quilt sizes, worked out
The same arithmetic applied to the middle of each range in our quilt size chart, with 4 inches of overhang, 40 inches of usable cotton, half-inch backing seams and 2.5-inch binding strips.
| Quilt | Cut backing (in) | Quilting cotton | 108 in wide | Binding |
|---|---|---|---|---|
| Baby / crib (40 × 52) | 48 × 60 | 2¾ yd2 lengths, horizontal | 1¾ yd1½ yd turned sideways | 6 strips, ½ yd |
| Lap / throw (60 × 72) | 68 × 80 | 4½ yd2 lengths, vertical | 2¼ yd2 yd turned sideways | 8 strips, ¾ yd |
| Twin (68 × 90) | 76 × 98 | 5½ yd2 lengths, vertical | 2¾ yd2¼ yd turned sideways | 9 strips, ¾ yd |
| Twin XL (68 × 96) | 76 × 104 | 6 yd2 lengths, vertical | 3 yd2¼ yd turned sideways | 9 strips, ¾ yd |
| Full / double (82 × 92) | 90 × 100 | 7½ yd3 lengths, horizontal | 3 yd2½ yd turned sideways | 10 strips, ¾ yd |
| Queen (90 × 100) | 98 × 108 | 8¼ yd3 lengths, horizontal | 3 yd2¾ yd turned sideways | 11 strips, 1 yd |
| King (104 × 100) | 112 × 108 | 9 yd3 lengths, vertical | 6 yd3¼ yd turned sideways | 12 strips, 1 yd |
| California king (100 × 104) | 108 × 112 | 9 yd3 lengths, horizontal | 3¼ yd | 12 strips, 1 yd |
The 108-inch column keeps the print upright; where turning the fabric sideways saves yardage, that figure is shown underneath. The lap row needs 4½ yards once the backing seam is sewn: two 40-inch lengths cover 79 inches, one short of the 80-inch cut.
How the backing math works
- Cut size. Add the overhang to every side: a 4-inch overhang adds 8 inches to both the width and the length. Four inches is what longarm quilters usually ask for; when you quilt on your own machine, two to three is enough. Ask your longarmer rather than guessing.
- Usable width. Quilting cotton comes off the bolt around 42 to 44 inches wide and loses its selvedges, which leaves roughly 40 inches you can seam. A single-piece backing can use the full width, because the edges are trimmed away after quilting anyway.
- Count the lengths. Each seam takes a seam allowance from both pieces it joins, so two 40-inch lengths joined with a half-inch seam cover 79 inches, not 80.
- Try both directions. Vertical seams: the lengths run down the quilt. Horizontal seams: they run across it. Multiply the number of lengths by how long each one is, divide by 36 and round up to the next quarter yard. The cheaper layout wins unless the print has a direction.
How the binding math works
- Go around the edge. Twice the width plus twice the length, then add about 10 inches for the starting tail, the closing join and the mitred corners.
- Cut strips across the fabric. Strips are cut selvedge to selvedge, so each one is as long as the usable width, about 40 to 42 inches.
- Allow for the joins. Strips are joined on the diagonal so the seam does not make a lump, and each join uses about one strip width of length. That is why five 40-inch strips give 190 inches, not 200.
- Buy the strips. Strip count times strip width is the fabric you need; round it up to the next quarter yard. This is the method our quilted lap throw uses: 168 inches of edge, 178 with the allowance, 5 strips, half a yard.
Frequently asked
How much fabric do I need for a quilt backing?
Add an overhang to every side of the finished top, four inches if a longarm quilter is finishing it or two to three if you quilt it yourself. Then count how many lengths of fabric it takes to cover that width, multiply by the length and round up to the next quarter yard. A queen top of 90 by 100 inches needs a 98 by 108 inch backing: 8¼ yards of standard quilting cotton, or 3 yards of 108-inch wide backing.
How many binding strips do I need for a quilt?
Measure all four sides, add about 10 inches for the starting tail, the closing join and the corners, then divide by the usable width of fabric, allowing about one strip width for each diagonal join. Our 36 by 48 inch lap throw needs 178 inches, which is 5 strips of 2.5 inches cut across 40 to 42 inches of usable width.
Should backing seams run vertically or horizontally?
Whichever uses less fabric, unless the print has a direction. Vertical seams keep the fabric's length running down the quilt; horizontal seams turn it sideways, which is often cheaper on a quilt that is wider than it is long but puts a directional print on its side. The calculator works out both and shows you the difference.
How wide should binding strips be?
Our quilting project cuts 2.5-inch strips and folds them in half lengthwise for a double-fold binding. Narrower strips give a slimmer edge and wider ones suit a thick batting; the calculator accepts any width and recalculates the strip count and yardage.
Is 108-inch wide backing worth it?
Often, for anything bed-sized. It covers most quilts in one piece with no seam, and the yardage drops sharply: a queen falls from 8¼ yards of regular cotton to 3 yards of wide backing. It costs more per yard and usually less per quilt, so compare the two totals rather than the price per yard.
Where to go next
Cutting a quilt goes faster with a rotary cutter, a long quilting ruler and a cutting mat; the batting shelf lists package sizes. New to quilting? Start with the beginner quilting guide.