Quilt math · Calculator
Quilt backing calculator
How much fabric to buy for the back of your quilt, and which way to seam it. Pick a size and the width of your fabric: the answer is worked out to the ⅛ yard.
The short answer
Make the backing 4″ bigger than the quilt top on every side. For a 60″ × 72″ throw that’s 68″ × 80″: 4½ yd of 42″ fabric, as two widths with one seam down the middle, or 2 yd of 108″ wide backing.
Work out yours
Free · no accountYour backing: 68″ × 80″
Quilt top 60″ × 72″ + 4″ on every side
2 widths of 80″, one seam down the length.
3 widths of 68″, 2 seams across.
One piece 68″ long, no seams. Costs more a yard.
Designing this quilt? Quarter Inch works out the backing, batting and binding with every fabric in the top, and keeps them right when you change the size.
Start a 60″ × 72″ quiltSame sums as the app: @quarterinch/cutting, backingOf · 4″ overhang · ½″ seams · up to the next ⅛ yd
How it’s worked out
Here’s the throw from the short answer, step by step. You can check every line with a pencil.
| The quilt top | 60″ × 72″ |
|---|---|
| Add 4″ on every side (8″ to each measurement) | 68″ × 80″ |
| Each width of 42″ fabric, less 2″ of selvages | 40″ |
| Widths side by side to reach 68″ across (two widths and a ½″ seam make 79½″) | 2 × 80″ |
| Fabric to buy: 160″, or 4.44 yd | 160″ |
| Up to the next ⅛ yd | 4½ yd |
Down the middle or across?
Seamed down the middle, the widths run the length of the quilt, side by side. Seamed across, they lie on their sides and stack. The calculator tries both and picks the one that uses less fabric.
For the throw, two widths reach 79½″: enough across the 68″ backing, but ½″ short of its 80″ length. So seamed across it needs a third width and 5¾ yd. With 44″ fabric (42″ to sew), two widths reach 83½″ and seams across wins: 3⅞ yd. Try it above.
When 108″ wide is cheaper
Wide backing comes 108″ across, 106″ once the selvages are off. When the backing is no wider than that one way, you need just one piece, as long as the other way: 2 yd for the throw. It costs more a yard, but there’s no seam to sew.
A king backing of 116″ × 116″ is too big for one piece. Use two widths of wide fabric (6½ yd), or three of ordinary 42″ fabric (9¾ yd).
Backing for every bed size
Each backing is 8″ bigger than the top each way. The 42″ and 44″ columns give the cheaper of the two seamed ways and how many widths: “2 down” is two widths seamed down the middle.
| Quilt top | Backing | 42″ fabric | 44″ fabric | 108″ wide |
|---|---|---|---|---|
| Crib 36″ × 48″ | 44″ × 56″ | 2½ yd · 2 across | 2½ yd · 2 across | 1¼ yd |
| Throw 60″ × 72″ | 68″ × 80″ | 4½ yd · 2 down | 3⅞ yd · 2 across | 2 yd |
| Twin 66″ × 90″ | 74″ × 98″ | 5½ yd · 2 down | 5½ yd · 2 down | 2⅛ yd |
| Queen 90″ × 96″ | 98″ × 104″ | 8¼ yd · 3 across | 8¼ yd · 3 across | 2¾ yd |
| King 108″ × 108″ | 116″ × 116″ | 9¾ yd · 3 down | 9¾ yd · 3 down | 6½ yd · 2 down |
What changes the answer
- Your quilter. Longarm quilters often ask for more than 4″ on every side. Ask, and set the extra to match. See working with a longarm quilter.
- Pre-washing. Fabric washed first shrinks, so you need a little more. How much extra to buy.
- Your fabric’s real width. Measure it from selvage to selvage. Two inches either way can change how many widths you need. More in width of fabric explained.
Questions
Short answers.
Something else? A real person replies.
hello@quarterinch.app
How much bigger than the top should a backing be?
We add 4″ on every side, which is 8″ to each measurement. It gives room to baste and quilt without running out at the edges. If someone else is quilting it, use the extra they ask for.
Why 40″, when my fabric is 42″ wide?
The selvages are woven tighter than the rest of the fabric and can pucker a seam, so we trim them off: about 1″ each side. If your fabric is wider, choose 44″ in the calculator.
How much backing do I need for a queen quilt?
For a 90″ × 96″ queen, the backing is 98″ × 104″: 8¼ yd of 42″ fabric as 3 widths, across, or 2¾ yd of 108″ wide.
Can I piece a backing from leftover fabric?
Yes. Sew the pieces into panels at least as big as the backing size the calculator gives, with ½″ seams pressed open.
Is 108″ wide backing worth it?
It costs more a yard, but often less in all, and there’s no seam to sew or show through. For anything up to a queen it’s one piece.