QuickCheckTools

Quilt backing calculator

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Enter your finished quilt top size to see how much backing fabric to buy, the seams you'll need, and the 108" wide option.

Worked example

A 58" × 66" quilt top, adding 4" on every side (from Missouri Star Quilt Co.'s published method):

  1. Backing size: 58 + 8 = 66" wide, 66 + 8 = 74" long.
  2. Widths: 66 ÷ 40 = 1.65, round up to 2 widths of fabric.
  3. Seams lengthwise: 2 × 74" = 148" ÷ 36 = 4.1, round up to 4¼ yards.
  4. Seams crosswise: 2 × 66" = 132" ÷ 36 = 3.7, round up to 3¾ yards (less fabric).
  5. 108" wide backing: 74" ÷ 36 = 2.06, round up to 2¼ yards, no seams.

Questions

How much bigger should quilt backing be than the top?

Add 4" on every side, so 8" to both the width and the length. Longarm quilters usually ask for 4" to 6" per side, and hand or small-machine quilting can use 2". Check with your longarmer before you buy.

How do I calculate quilt backing yardage?

Add the extra to the width and length. Divide the backing width by 40" (the usable width of 42" quilting cotton once selvages are trimmed) and round up: that is how many fabric widths you sew together. Multiply by the backing length, divide by 36" and round up to the next ¼ yard.

Should the backing seams run lengthwise or crosswise?

Whichever needs less fabric, unless the print is directional. Crosswise seams often save fabric on quilts under about 60" wide. This calculator shows both and marks the smaller one.

How much 108" wide backing do I need?

If your backing width fits across the 108" fabric, buy the backing length. A 58" × 66" quilt needs a 66" × 74" backing, so 74" of 108" fabric: 2¼ yards, with no seams.

How much backing for a queen quilt?

A 90" × 95" queen top needs a 98" × 103" backing. With seams down the length that is three widths of 42" fabric, 309" in total: 8¾ yards. With seams across it is three widths of 98", 294" in total: 8¼ yards. On 108" wide backing it is 3 yards with no seams.

Does this include shrinkage?

No. If you prewash, add about 5% for shrinkage, or round up to the next ¼ yard to be safe.

Assumes 42" quilting cotton with 40" usable after trimming selvages (112cm with 102cm usable in metric). Checked against Missouri Star Quilt Co.'s worked example and its backing chart for crib to California king.