Guide

How to calculate quilt backing

Make the backing 8″ bigger than the quilt top in both directions (4″ on each side), divide the width by the usable width of your fabric (about 42″) and round up to get the number of widths, then multiply by the length. For a 90″ × 108″ queen quilt that is 3 widths of 98″, or 8¼ yd of 42″ fabric.

The calculation

Add the extra. Quilt width + 8″, quilt length + 8″. For a 90″ × 108″ queen: 98″ × 116″.
Count the widths. Most quilting cotton is 42–44″ wide with about 42″ usable once the selvages are trimmed. Each seam takes 1″ (½″ seams, pressed open). One way: 98″ ÷ 42″ = 3 widths. The other way: 116″ ÷ 42″ = 3 widths.
Multiply by the length. 3 widths seamed across, each 98″ long = 294″. Or 3 widths seamed down, each 116″ long = 348″. Take the smaller one.
Convert to yards and round up to the next ⅛: 294″ ÷ 36 = 8⅛ → 8¼ yd.

Backing chart

Quilt	Size	Backing size	42″ fabric	108″ wide
Crib	36″ × 52″	44″ × 60″	2½ yd (2 widths of 44″)	1¼ yd
Throw	60″ × 70″	68″ × 78″	3⅞ yd (2 widths of 68″)	2 yd
Twin	70″ × 90″	78″ × 98″	5½ yd (2 widths of 98″)	2¼ yd
Full / double	85″ × 108″	93″ × 116″	7¾ yd (3 widths of 93″)	3¼ yd
Queen	90″ × 108″	98″ × 116″	8¼ yd (3 widths of 98″)	3¼ yd
King	108″ × 108″	116″ × 116″	9¾ yd (3 widths of 116″)	6½ yd

Questions

How much bigger should backing be than the quilt top?

At least 4″ on every side, so 8″ wider and 8″ longer. Longarm quilters often ask for 4–6″ per side. Check with yours before you buy.

Should backing seams run across or down?

Either works. Pick whichever uses less fabric: for most queens, three widths seamed across the quilt use less than two down its length. Press the seams open to keep them flat.

Is 108″ wide backing worth it?

For big quilts, often yes: no seams, and a queen needs 3¼ yd instead of 8¼ yd. It costs more per yard, so compare the total. A king (116″ wide with the extra) still needs two lengths of 108″ fabric.

Updated November 9, 2026