Quilting calculator
Quilt Backing Calculator: 42" or 108" Wide Back Yardage
How much backing fabric you need from 42-inch quilting cotton or a 108-inch wide back, with panels, seam direction and a yardage chart by quilt size.
Your quilt
Backing fabric to buyExample: 84 in × 92 in quilt
7 3/4 yd
Horizontal seams: 3 panels of quilting cotton (40 in usable), 92 in long.
- Backing size
- 92 in × 100 in
- Horizontal seams
- 7 3/4 yd
- Vertical seams
- 8 3/8 yd
- Wide back
- 2 5/8 yd
- Cost
- Wide back is cheaper below 2.95 × the 42 in price per yard
Each amount is rounded up to the next 1/8 yd.
Backing shopping list
- Backing, quilting cotton (40 in usable) 7 3/4 yd
- Cut into 3 panels × 92 in
| Layout | Buy | Cost | Cut |
|---|---|---|---|
| Horizontal seams | 7 3/4 yd | – | 3 × 92 in |
| Vertical seams | 8 3/8 yd | – | 3 × 100 in |
| Wide back | 2 5/8 yd | – | 1 × 92 in |
Backing yardage by quilt size
| Quilt | 40 in fabric | Wide back |
|---|---|---|
| Crib36 × 52 in91.4 × 132.1 cmBacking 44 × 60 in111.8 × 152.4 cm | 2 1/2 yd2 × 44 in, horizontal seams | 1 1/4 yd |
| Baby36 × 56 in91.4 × 142.2 cmBacking 44 × 64 in111.8 × 162.6 cm | 2 1/2 yd2 × 44 in, horizontal seams | 1 1/4 yd |
| Throw / lap50 × 65 in127 × 165.1 cmBacking 58 × 73 in147.3 × 185.4 cm | 3 1/4 yd2 × 58 in, horizontal seams | 1 5/8 yd |
| Twin63 × 87 in160 × 221 cmBacking 71 × 95 in180.3 × 241.3 cm | 5 3/8 yd2 × 95 in, vertical seams | 2 yd |
| Twin XL70 × 95 in177.8 × 241.3 cmBacking 78 × 103 in198.1 × 261.6 cm | 5 3/4 yd2 × 103 in, vertical seams | 2 1/4 yd |
| Full / double78 × 87 in198.1 × 221 cmBacking 86 × 95 in218.4 × 241.3 cm | 7 1/4 yd3 × 86 in, horizontal seams | 2 1/2 yd |
| Queen84 × 92 in213.4 × 233.7 cmBacking 92 × 100 in233.7 × 254 cm | 7 3/4 yd3 × 92 in, horizontal seams | 2 5/8 yd |
| King100 × 92 in254 × 233.7 cmBacking 108 × 100 in274.3 × 254 cm | 8 3/8 yd3 × 100 in, vertical seams | 3 yd |
| California king96 × 96 in243.8 × 243.8 cmBacking 104 × 104 in264.2 × 264.2 cm | 8 3/4 yd3 × 104 in, horizontal seams | 3 yd |
https://homedosh.com/quilt-backing-calculator/
How this is calculated
The backing needs to be bigger than the quilt top: we add the extra you choose to every side. 4 in is the minimum; many longarm quilters want more, so ask yours. Quilting cotton is narrower than most quilts, so it is sewn from panels. We count the fewest panels that cover the backing after the seams, for seams running across (horizontal) and down (vertical), and compare that with one piece of wide back. If one piece of wide back is not wide enough, use a wider back (118 to 120 in) or add a strip. Each amount is rounded up to the next 1/8 yd. With prices we recommend the cheapest; without them, the layout with the least 40 in fabric, plus the price ratio at which wide back wins.
Steps for your numbers
- Backing size = quilt + 2 × 4 in overhang = 92 in × 100 in
- Horizontal seams: 3 panels × 92 in = 276 in → 7 3/4 yd
- Vertical seams: 3 panels × 100 in = 300 in → 8 3/8 yd
- 106 in wide back: 1 panel × 92 in = 92 in → 2 5/8 yd
Prewashing? Enter the expected shrinkage under More options. We plan with the narrower width and add the lost length back.
Questions and answers
How much fabric do I need for a queen quilt backing?
For an 84 × 92 in queen quilt with 4 in extra on every side, the backing is 92 in × 100 in. With 40 in usable fabric that is 7 3/4 yd (3 panels, horizontal seams), or 2 5/8 yd of 108 in wide back.
Should I use 42 in quilting cotton or a 108 in wide back?
Wide back means no seams and less cutting. For the queen example it is cheaper when its price per yard is below 2.95 × the price of your 42 in fabric. Enter both prices in the calculator to compare.
Horizontal or vertical seams?
Both work. The calculator shows the layout that needs less fabric. For the queen example, horizontal seams take 7 3/4 yd and vertical seams 8 3/8 yd.
How much bigger than the quilt top should the backing be?
At least 4 in on every side, and 4 to 6 in more if your quilter uses clamps or leader grips (APQS). The Fat Quarter Shop backing chart asks for at least 10 in larger in width and length. 4 in is the minimum: ask your longarm quilter and enter their number under More options.
Why does the calculator use 40 in fabric width?
Quilting cotton is 42 to 44 in on the bolt, but after trimming the selvages and prewashing about 40 in is usable. APQS and Missouri Star calculate with 40 in. Measure your fabric and change the width if yours is wider.
Sources
- APQS: get the perfect backing yardage (1/2 in seams)
- APQS: how to load a quilt (at least 4 in extra per side, more with clamps)
- Fat Quarter Shop: quilt backing reference chart (at least 10 in larger)
- Fat Quarter Shop: quilt sizes guide
- Missouri Star: quilt sizes chart
- NIST Handbook 44, Appendix C (inch, yard, meter)
Checked on 2026-11-03.