Backing is the layer most likely to surprise you at the cutting table, because anything wider than your fabric has to be pieced. This calculator sizes the backing with overhang, tells you how many widths to seam, and gives you the yardage to buy.
How quilt backing yardage is calculated
The backing has to be larger than the quilt top so there is something to grab while you baste and quilt. We start by adding the overhang to all four sides, then decide whether the backing fits within a single fabric width or needs piecing.
- Backing width = quilt width + (2 × overhang)
- Backing height = quilt height + (2 × overhang)
- If backing width ≤ fabric width: one panel; yardage = backing height ÷ 36, rounded up to the nearest 1/8 yard.
- If backing width > fabric width: widths needed = backing width ÷ fabric width, rounded up; yardage = (backing height ÷ 36) × widths needed, rounded up to the nearest 1/8 yard. Seam those widths together.
For example, a 60" × 72" quilt with 4" overhang needs a backing of 68" × 80". On 42" fabric that is wider than one width, so you need 2 widths seamed together and roughly 4½ yards. On 108" wide backing it fits in a single panel with no seams.
Wide backing fabric avoids seams
Standard quilting cotton is about 42–44" wide, so any quilt wider than a crib quilt usually needs the backing pieced from two or more widths. Wide backing fabric, sold at 108" (and sometimes 90"), is made specifically to back quilts in a single seamless panel. It costs more per yard but saves cutting, seaming, and the bulk of a center seam — a real advantage if you send quilts to a longarm quilter.
Pro tip: When you do seam standard fabric, press the seam open rather than to one side. An open seam is half as bulky and far easier to quilt across, especially on a longarm.
Tips for buying backing fabric
- Give yourself overhang. Four inches per side is the common minimum; ask your longarm quilter if they want more.
- Square it up. Tear or cut backing on grain so it hangs straight and doesn't distort the quilt.
- Buy a little extra. Prewashing and squaring eat into yardage, so an extra quarter yard is cheap insurance.
- Consider the seam direction. Whichever orientation uses less fabric is the one to choose — for tall quilts that is usually vertical seams.
Let Quiltler 3 do it for you: Quiltler 3 figures out backing, batting, binding, and every block fabric automatically for your full quilt design, then exports a PDF cutting guide. Explore the all-in-one fabric calculator to plan your whole project at once.