How Much Fabric Do You Need for a Quilt Backing and Binding?

The top of a quilt gets all the planning: the blocks, the colours, the layout. The backing and binding are often bought last, in a hurry, and that is when people discover that a quilt back is wider than any ordinary fabric and needs seams, or that the binding strips come up a few centimetres short. This guide works through the fabric for a quilt's backing and binding with real numbers, using the site's Fabric Yardage Calculator and Fabric Shrinkage Calculator, and shows why for backings you should count whole widths rather than trust an area estimate.

Size the backing larger than the top

The backing must be bigger than the quilt top on every side. Quilting, by hand or machine, draws the layers in slightly, and a longarm quilting machine needs extra fabric to clamp. A common allowance is around 10 cm on each side for home machine quilting, often more for longarm quilting; if someone else is quilting it for you, ask what they need.

For the worked example: a quilt top of 150 cm by 200 cm, with 10 cm extra on each side, needs a backing of 170 cm by 220 cm.

Option 1: standard-width quilting cotton

Quilting cotton is usually about 112 cm wide, with roughly 108 cm usable after trimming the selvedges. A 170 cm wide backing is wider than that, so it must be pieced from more than one width.

Counting widths: 170 cm needs two widths of 108 cm (one width is not enough, two give 216 cm, more than enough). Each width must be as long as the backing, 2.2 m. So the fabric to buy is 2 × 2.2 m = 4.4 m, joined with one long seam down the back. You could instead run the seam across the quilt, using widths laid sideways; for this size that needs the same or more fabric, but for some sizes a horizontal seam saves a length.

What the area method says: the backing is 3.74 m². The yardage calculator, with 108 cm usable width, gives 3.46 m with no waste, or 3.81 m with a 10% allowance. Both are well short of the 4.4 m you actually need, because the second width is only partly used: 216 cm of fabric width for a 170 cm backing. The leftover 46 cm strip, 2.2 m long, is not waste exactly, since it can go into the binding or a pieced back, but you still have to buy it.

This is the general lesson for any piece wider than the fabric: count whole widths, and treat the area method as a lower bound.

Option 2: extra-wide backing fabric

Many shops sell backing fabric around 270 to 280 cm wide, often sold as 108 inches (274.32 cm). With 270 cm usable, the backing fits in a single width. The length needed is the width of the backing along the roll: either 1.7 m or 2.2 m, depending on which way you lay it. Laid with its 170 cm side along the roll, you buy 1.7 m. The yardage calculator gives 1.39 m for 3.74 m² at 270 cm, but again the rectangle shape decides: you need a 1.7 m length to get a 170 cm dimension, whatever the area says.

Extra-wide backing avoids a seam, which many quilters prefer for longarm quilting and for the look of the back. It usually costs more per metre than standard quilting cotton, but you buy far less length, so compare the cost of the whole backing, not the price per metre.

Binding

Binding is a long strip folded over the quilt's raw edges. To work out how much fabric it needs:

1. Find the perimeter of the quilt top: (150 + 200) × 2 = 700 cm.
2. Add an allowance for joining the ends and turning the corners. Around 25 cm is common: 725 cm in total.
3. Choose the strip width. Double-fold binding is often cut at about 6 to 6.5 cm wide; follow your pattern or preference. Here: 6.5 cm.
4. Count strips cut across the width. Each strip cut selvedge to selvedge gives about 108 cm of usable length. 725 ÷ 108 = 6.7, so cut 7 strips.
5. Fabric length = number of strips × strip width = 7 × 6.5 cm = 45.5 cm. Buy at least 50 cm to allow for squaring the edge.

Bias binding, cut at 45 degrees, stretches round curves and wears well on edges, but takes more fabric and more cutting. For straight-edged quilts, binding cut across the width is the usual choice.

Shrinkage and pre-washing

Whether to pre-wash quilting fabrics is a long-running debate, covered in the guide to pre-washing fabric. For the backing, the main point is consistency: if the top is pre-washed and the backing is not, or the other way round, the layers can shrink differently in the first wash and pucker.

If you do pre-wash the backing, allow for the shrinkage when buying. With a measured 3% shrinkage, the shrinkage calculator's pre-cut mode turns the 220 cm length of each width into 226.8 cm, and the 4.4 m order into 4.54 m. Width shrinkage matters too: two widths of 108 cm have plenty of spare here, but on a backing that only just fits, a few centimetres lost across the width could leave the back too narrow.

Wadding (batting)

The wadding, or batting, sits between top and back and is usually sold in widths and pre-cut sizes designed for quilts. Cut it to the backing size or a little smaller. Cotton waddings can shrink noticeably in the first wash, which gives an antique crinkled look; polyester waddings shrink very little. Read the manufacturer's notes on shrinkage and on maximum quilting distance, which tells you how far apart the lines of quilting can be.

Weight of the finished quilt

A quilt is heavier than it looks. The quilting cotton in a quilt like this is typically somewhere around 150 GSM, which the Fabric Weight Converter shows as 4.42 oz/yd². The Fabric Weight from Dimensions tool will turn the backing's area and GSM into a weight, to which you add the top, the wadding and the binding. That matters for posting a quilt, and for washing it: a large quilt can be too heavy for a domestic machine when wet.

Summary of the example

• Quilt top 150 x 200 cm; backing 170 x 220 cm.
• Standard 112 cm fabric: 2 widths of 2.2 m = 4.4 m, one seam (4.54 m with 3% shrinkage).
• Extra-wide 274 cm backing: 1.7 m, no seam.
• Binding: 725 cm, 7 strips of 6.5 cm = 45.5 cm, buy 50 cm.

What the calculators cover

The yardage calculator converts area into length for a given width and is a quick lower bound for backing fabric. It does not know that a backing has to be one rectangle, so for any piece wider than your fabric, count whole widths. The shrinkage calculator adds the allowance for a measured shrinkage. The rest, longarm allowances, seam placement, binding width, is a matter of method and preference.