This quilt backing calculator works out how much fabric to buy for the back of a quilt, how many panels to cut and whether the seams should run up and down or across. Enter the finished quilt size and the extra each side your quilter needs, and you get the yardage for standard 42″ cotton or 108″ wide backing.
Enter the quilt width and length to see yardage. If you leave the extra blank, the calculator uses 4″ per side; if you leave the usable width blank, it uses the usable width of the fabric you picked. Assumes selvages trimmed off and 1/2″ seams joining panels (1″ used per seam). Yardage is rounded up to the next 1/8 yard. Add extra if you need to match a print or prewash fabric that may shrink.
How the Quilt Backing Calculator Works
A quilt back has to be bigger than the top, because the layers shift a little during quilting and a longarm frame needs fabric to clamp onto. The tool adds your chosen extra to every side, then checks how many widths of fabric it takes to cover that area. It tries two layouts, with panels running the length of the quilt and with panels running across it, and recommends the one that uses less fabric. Seams take up an inch each, so three 40″ panels cover 118″, not 120″.
Formula: Backing width = Quilt width + 2 × Extra. Backing length = Quilt length + 2 × Extra. Panels = (Span to cover − 1) ÷ (Usable width − 1), rounded up. Lengthwise layout fabric = Panels × Backing length. Crosswise layout fabric = Panels × Backing width. Yardage = Fabric in inches ÷ 36, rounded up to the next 1/8 yard, using the smaller of the two layouts.
- Quilt width and Quilt length — the finished size of the quilt top, in inches, measured through the middle.
- Extra on each side — how much larger the backing must be on every edge. Longarm quilters often ask for 4″ to 6″; for hand or domestic machine quilting, 2″ to 4″ is typical. If you leave it blank, the calculator uses 4″.
- Backing fabric — presets for 42-44″ cotton, 60″ fabric and 108″ wide backing; the matching usable width applies when the next box is blank.
- Usable fabric width — optional; the width left after trimming selvages. Measure your actual bolt if you can, since widths vary. If you leave it blank, the calculator uses the usable width of the fabric you picked.
Example Scenarios
| Quilt size | Extra per side | Usable width | Backing size | Layout | Yardage |
|---|---|---|---|---|---|
| 60″ x 80″ | 4″ | 40″ | 68″ x 88″ | 2 panels of 88″, lengthwise seam | 5 yd |
| 50″ x 65″ | 4″ | 40″ | 58″ x 73″ | 2 panels of 58″, crosswise seam | 3 1/4 yd |
| 90″ x 108″ | 4″ | 40″ | 98″ x 116″ | 3 panels of 98″, crosswise seams | 8 1/4 yd |
| 90″ x 108″ | 4″ | 104″ (108″ wide) | 98″ x 116″ | 1 piece of 116″, no seams | 3 1/4 yd |
| 36″ x 36″ | 2″ | 40″ | 40″ x 40″ | 1 piece of 40″, no seams | 1 1/8 yd |
How Much Fabric for Quilt Backing: Tips and Common Mistakes
The usual mistake is buying yardage for the quilt top size and forgetting the overhang. A 60″ x 80″ quilt looks like it needs two lengths of 80″, but with 4″ all round you need two lengths of 88″, and the quilt backing calculator rounds that up to 5 yards. Here are more ways to get it right the first time.
- Ask your quilter first. Requirements for quilt backing for longarm work vary by shop, and some want 6″ or even 8″ per side on large quilts.
- Measure the finished top, not the pattern size. Borders often finish an inch or two different from the instructions.
- Use a wide back fabric calculator setting for queen and king quilts. One length of 108″ fabric often costs less time than three seamed panels, and it removes bulky seams from the back.
- Prewash or buy extra. Cotton can shrink a few percent, which eats into a tight overhang.
- Press seams open on pieced backs. Open seams lie flatter under the quilting and are less likely to show through.
Want a quilt backing yardage chart? The example table above covers common sizes, and you can run any custom size in seconds. For background on quilt layers and construction methods, see Wikipedia’s article on quilts and quilting layers.
Quilt Backing Calculator FAQ
How much fabric do I need for a quilt backing?
Add the extra your quilter needs to every side, usually 4″, then divide the backing width by the usable fabric width to get the number of panels. Multiply panels by the backing length and divide by 36 for yards. A 60″ x 80″ quilt with 4″ all round needs 5 yards of 42″ cotton.Is there a quilt backing calculator app?
You do not need to download a separate app. This quilt backing calculator runs in any phone or desktop browser and is free, with no account. Bookmark the page or add it to your home screen, and it works like an app when you are standing at the fabric counter deciding how many yards to buy.How does the calculator handle 108 inch wide backing?
Choose the 108″ wide back preset, which assumes about 104″ usable after trimming. Most quilts up to queen size then fit in one piece, so you only buy the backing length. A 90″ x 108″ quilt with 4″ overhang needs 116″ of fabric, or 3 1/4 yards of wide back.Should backing seams run vertically or horizontally?
Either works structurally. The calculator picks whichever layout uses less fabric. Lengthwise seams suit tall quilts with narrow widths, while crosswise seams often save yardage on wide quilts. Some longarm quilters prefer seams parallel to the rollers, so ask yours if you are sending the quilt out.How much extra backing does a longarm quilter need?
Most longarm quilters ask for 4″ to 6″ of extra fabric on every side, and some request more for king quilts or dense designs. The extra gives the frame something to clamp and allows for the quilt drawing up as it is stitched. Enter their figure in the Extra on each side field.Can I piece a backing from leftover fabric?
Yes. Pieced backs are common and use up stash fabric. Make sure the pieced panel reaches the full backing size shown in the results, press seams open and keep seams away from the exact centre if possible. Square up the finished back before layering so the edges are straight on the frame.Related Calculators
Planning more than the back? Work out square inches or yards of batting with the rectangle area calculator, convert metric pattern sizes with the inch to cm converter, and see how roll widths and seams add up with the wallpaper calculator for strips and drops, which uses the same panel logic as the quilt backing calculator.