Quilt Backing Calculator
Work out how much fabric the back of your quilt needs. Enter the size of the quilt top, the extra you want on each side and the fabric width, and the calculator compares vertical and horizontal seams and picks the layout that uses the least yardage.
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Longarm quilters usually ask for 4 in; 2–3 in is fine for a home machine.
Per panel edge; ½ in is common for backing seams.
Add 3–5% if you will pre-wash cotton.
How to use the Quilt Backing Calculator
- Enter the quilt top width and length in inches.
- Set the extra backing on each side: 4 in for a longarm quilter, 2–3 in at home.
- Choose the fabric width, seam allowance and any shrinkage allowance.
- Press Calculate backing to see the yardage, panels and seam layout.
- Cut the panels, remove selvedges, sew them together and trim to size.
How quilt backing yardage is calculated
Backing size = quilt top + 2 × overage on each dimension.
Vertical layout: number of widths = backing width ÷ usable fabric width (allowing for seams), each cut as long as the backing.
Horizontal layout: widths = backing length ÷ usable width, each cut as long as the backing is wide.
Yardage = widths × cut length ÷ 36, rounded up to the next ⅛ yard. The calculator picks the layout with less fabric.
Example: a 60 × 72 in throw with 4 in extra needs a 68 × 80 in backing. With 40 in usable cotton, vertical seams need 2 panels × 80 in = 160 in (4½ yd) and horizontal seams need 3 panels × 68 in = 204 in (5⅝ yd), so go vertical: 4½ yards cut into two 80 in lengths.
Backing for common quilt sizes
With 4 in extra on each side and ½ in seams.
| Quilt top | Backing size | 42–44 in cotton | 108 in wide back |
|---|---|---|---|
| Baby 36 × 52 in | 44 × 60 in | 2½ yd (2 panels, horizontal) | 1¼ yd (no seam) |
| Crib 45 × 60 in | 53 × 68 in | 3 yd (2 panels, horizontal) | 1½ yd (no seam) |
| Throw 60 × 72 in | 68 × 80 in | 4½ yd (2 panels, vertical) | 2 yd (no seam) |
| Twin 70 × 90 in | 78 × 98 in | 5½ yd (2 panels, vertical) | 2¼ yd (no seam) |
| Full 84 × 90 in | 92 × 98 in | 7¾ yd (3 panels, horizontal) | 2⅝ yd (no seam) |
| Queen 90 × 108 in | 98 × 116 in | 8¼ yd (3 panels, horizontal) | 3¼ yd (no seam) |
| King 108 × 108 in | 116 × 116 in | 9¾ yd (3 panels, horizontal) | 6½ yd (2 panels, horizontal) |
Backing tips
- Remove selvedges before seaming; they shrink differently and can pucker the back.
- Press seams open to reduce bulk where the quilting crosses them.
- Mark the top edge of a directional print so every panel runs the same way.
- Square the backing before loading it on a frame; a crooked back is the most common cause of tucks.
Frequently asked questions
How much bigger should quilt backing be than the top?
Most longarm quilters ask for 4 inches extra on every side, so the backing is 8 inches wider and 8 inches longer than the top. For quilting on a home sewing machine 2 to 3 inches per side is usually enough, but extra gives you room if the layers shift.
How much backing fabric do I need for a queen quilt?
A 90 × 108 inch queen top with 4 inches on each side needs a 98 × 116 inch backing. With 42–44 inch cotton that is three widths with horizontal seams, each 98 inches long, about 8¼ yards. With 108 inch wide-back fabric it is a single piece 116 inches long, about 3¼ yards.
Should backing seams run vertically or horizontally?
Either is fine for the quilt itself; choose the layout that uses less fabric. Vertical seams run the length of the quilt and are common on lap and twin quilts. Horizontal seams often save fabric on wider quilts. Longarm quilters generally prefer seams that run parallel to the rollers, so ask yours.
What is the usable width of quilting cotton?
Quilting cotton is sold as 42 to 44 inches wide including the selvedges. After trimming the selvedges and allowing for slightly crooked cuts, plan on about 40 inches. Wide-back fabrics sold as 108 inches usually give about 104 to 106 inches.
Why use a ½ inch seam on quilt backing?
Backing seams take more stress than piecing seams because the quilt is stretched on a frame. A ½ inch seam pressed open lies flatter and is stronger than a scant ¼ inch seam. The calculator subtracts the seam allowance from both panels at each seam.
Is wide-back fabric worth it?
For large quilts, a 108 inch wide backing often needs a third of the yardage of standard cotton and has no seams at all. It costs more per yard, so compare the total price of both options in the table.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.