How much backing fabric do I need for a quilt?

Add the overage to both sides of the quilt, then check whether that fits inside one usable width of 108-inch backing. A 60 × 70 inch quilt needs 68 × 78 inches, which fits one width and therefore one length of 78 inches — a little over two yards.

When does quilt backing need a seam?

When the quilt plus overage is wider than the usable width of the backing. Nominal 108-inch cloth is about 104 inches usable once the selvedges are off, so a quilt wider than roughly 96 inches needs two widths pieced and a seam down the back.

How much extra backing should I allow?

Four inches on every side is the longarm convention, because the machine needs room to clamp the layers. Three inches is the domestic-machine figure. Both are selectable here, and the answer changes: a 100-inch quilt fits one width at 3 inches of overage and needs two at 4.

How much fabric does quilt binding take?

The perimeter plus allowance for corners, joins and the finishing tail, divided into strips cut across the width of fabric. A 60 × 70 quilt has a 260-inch perimeter; with 20 inches of tail allowance that is 280 inches of binding, or seven strips at 40 inches usable width.

Quilting

Quilt backing & binding calculator

Work out how much cloth a quilt needs: the backing from the quilt size and overage, and the binding strips from the perimeter.

Why wide backing is the mill's business

Quilt backing is bought as wide cloth, and in quilting wide means 108 inches — 274 cm. That is inside the greige range this mill weaves, which is why a backing calculator belongs on a weaving site rather than a quilt shop. The two questions are always the same: will the back fit in one width of cloth or does it need a seam, and how many strips does the binding take.

Quilting

Work out how much cloth a quilt needs: the backing from the quilt size and overage, and the binding strips from the perimeter.

Backing

Backing needed: 68.0 in × 78.0 in

Widths of cloth

Cloth to buy

2.17 yd

2.17

Fits one width — no seam

Binding

Binding length: 280.0 in

Strips to cut

Cloth for binding

0.44 yd

Assumes a solid circular filament of cloth laid flat — that is, plain arithmetic on the size you enter. Nothing here is a measurement of your quilt.

108 in nominal, 104 in usable after 4 in of selvedge.

The arithmetic

Overage, usable width and tail allowance are conventions rather than standards — quilters differ, so all three are inputs here with the common value as the default.

backing width = quilt width + (overage × 2)
backing length = quilt length + (overage × 2)
widths = ⌈ backing width ÷ usable width ⌉
linear cloth = backing length × widths
binding strips = ⌈ (perimeter + 20 in) ÷ 40 in ⌉

Widths of cloth:: 108 in nominal / 104 in usable
Strips to cut:: 40 in usable width of fabric
Binding length:: +20 in tail allowance

Common questions

How much backing fabric do I need for a quilt?: Add the overage to both sides of the quilt, then check whether that fits inside one usable width of 108-inch backing. A 60 × 70 inch quilt needs 68 × 78 inches, which fits one width and therefore one length of 78 inches — a little over two yards.
When does quilt backing need a seam?: When the quilt plus overage is wider than the usable width of the backing. Nominal 108-inch cloth is about 104 inches usable once the selvedges are off, so a quilt wider than roughly 96 inches needs two widths pieced and a seam down the back.
How much extra backing should I allow?: Four inches on every side is the longarm convention, because the machine needs room to clamp the layers. Three inches is the domestic-machine figure. Both are selectable here, and the answer changes: a 100-inch quilt fits one width at 3 inches of overage and needs two at 4.
How much fabric does quilt binding take?: The perimeter plus allowance for corners, joins and the finishing tail, divided into strips cut across the width of fabric. A 60 × 70 quilt has a 260-inch perimeter; with 20 inches of tail allowance that is 280 inches of binding, or seven strips at 40 inches usable width.