Quilt Backing Calculator
Enter your quilt size and this free calculator tells you exactly how many yards of backing fabric to buy, how many panels to cut, and which direction the seams should run. It checks both seam directions, plus the diagonal seam method, and picks the one that wastes the least fabric.
How backing yardage is calculated
The math behind the calculator is the same method quilt shops use at the cutting counter:
- Add overage. Your overage is added to all four sides. A 60 × 80" quilt with 4" overage needs a 68 × 88" piece of backing.
- Count panels. If the needed piece is wider than your fabric, panels are joined with ½" seams. Each seam eats 1" of combined width, and the calculator accounts for it.
- Check both directions. Panels can run parallel to the quilt's length (vertical seams) or its width (horizontal seams). One direction almost always needs less fabric, so the calculator compares both and gives you the cheaper cut.
- Try a diagonal seam. For smaller backings (up to about 1.5 times the fabric width), one length cut corner to corner and slid wider often beats two full panels. This is John Flynn's diagonally pieced method. Best fit uses it automatically when it saves fabric, or you can pick it yourself.
- Round up. The final number is rounded up to the next ⅛ yard, the way fabric is actually sold.
Backing yardage for common quilt sizes
Calculated with this tool using 4" overage per side and standard 42" usable-width quilting cotton:
| Quilt size | Dimensions | Backing needed | Panels |
|---|---|---|---|
| Crib | 36 × 52" | 1 ⅞ yd | 1 piece, diagonal seam (2 ½ yd with straight seams) |
| Throw | 50 × 65" | 3 ¼ yd | 2, horizontal seam |
| Twin | 70 × 90" | 5 ½ yd | 2, vertical seam |
| Queen | 90 × 95" | 8 ¼ yd | 3, horizontal seams |
| King | 108 × 108" | 9 ¾ yd | 3 panels |
On 108" wide backing, every size in this table needs zero seams: buy the quilt length plus 8" and you are done.
Backing questions, answered
How much fabric do I need for a quilt backing?
Add 4 inches of overage to every side of your quilt, then divide that width by your usable fabric width to find how many panels you need to join. For a 60 by 80 inch quilt on standard 42 inch quilting cotton, that works out to 2 panels and about 5 yards of fabric.
Why do I need extra backing fabric around the quilt?
The backing must be larger than the quilt top so the layers can be basted and quilted without running out of fabric at the edges. Most long-arm quilters ask for 4 inches of extra backing on every side. If you quilt on a domestic machine, 2 to 3 inches per side is usually enough.
Should backing seams run vertically or horizontally?
Whichever direction uses less fabric. Running panels parallel to the longer side often saves a full panel. This calculator checks both directions automatically and picks the one that needs fewer total yards.
What is a diagonally pieced quilt backing?
Instead of sewing two full panels side by side, you cut one length of fabric corner to corner, slide one half along the cut until the piece is wide enough, and sew the diagonal back together. The piece gets wider and shorter, so one length can cover a backing up to about 1.5 times the fabric width. It saves fabric on crib, baby, and small throw quilts. The method was devised by John Flynn. Choose Diagonal seam in the calculator to get the cut length and step-by-step instructions.
Is 108 inch wide backing worth it?
For most quilts up to king size, 108 inch wide backing eliminates seams entirely: you buy one length and you are done. It usually costs more per yard than 42 inch cotton, but you need far fewer yards and skip the piecing. Enter 108 as the fabric width above to compare.
How wide is quilting cotton really?
Quilting cotton is sold as 44/45 inch, but after washing and removing selvages you can usually count on 42 inches of usable width. This calculator defaults to 42 so your estimate stays on the safe side.
This is one of seven calculators inside Makerly.
The free version does one job well. Inside Makerly, the calculators work together: enter your quilt size once and backing, batting, binding, borders, on-point, yardage, and a full printable cut list all update from the same numbers.
- Save every quilt as a project, with its numbers attached
- Design the quilt first in the Block Designer, then let the math follow
- Track your fabric stash so you know what you already own
- Works in your browser and on iPhone and Android, always in sync
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