How much fabric do I need for a quilt?

Nearly every quick yardage estimate works from area: add up the square inches of every piece, divide by 1,584 (the square inches in a yard of 44″ fabric), add a fudge factor. It is fast and it is wrong, usually by a lot — because you cannot cut a quilt from area. You cut it from strips.

Fabric is bought in strips, not squares

Say you need forty 5″ squares. From 40″ of usable width you get eight squares per strip, so you need five strips at 5″ each — 25″ of fabric, or ¾ yard. The area calculation says 40 × 25 = 1,000 square inches, which is 0.63 yards. The difference is the eight inches at the end of each strip that are too narrow to be another square.

Now make it forty 6″ squares. Six per strip, so seven strips, 42″, or 1¼ yards. The area method says 0.91 yards. Every awkward size widens the gap, and quilts are full of awkward sizes.

FourPatch packs every piece into strips the way you would at the cutting table — a first-fit-decreasing bin pack, one bin per strip height — so the number it gives you is the number of inches you actually pull off the bolt.

Usable width

Quilting cotton is sold as 42–44″ wide, but that includes the selvedges, which you cut off, and cotton that has been through a wash and a dryer will have drawn in. Forty inches usable is a safe working assumption and is what FourPatch defaults to. If you never prewash and you trust your supplier, 42″ is defensible. If you prewash, drop to 40″ and do not regret it.

Waste allowance

A 10% allowance on top of the calculated yardage covers cutting errors, a directional print that needs to be positioned, a fabric that turns out to have a flaw, and the piece you cut wrong at eleven at night. For a fabric you can easily buy more of, 10% is plenty. For a fabric from a bundle, a fat quarter you loved, or anything discontinued, buy 20% and sleep.

Backing

Backing is where the biggest single number in your fabric list comes from, and where the seam direction matters most. Anything wider than about 40″ needs two panels, and the choice between a vertical and a horizontal seam can be more than a yard apart on the same quilt.

The rule: multiply the number of panels by the length of each panel, in both orientations, and take the smaller. The quilt size chart has this worked out for every standard size. Extra-wide 108″ backing removes the decision entirely and usually costs about the same.

Binding

Perimeter of the quilt, plus 12″ for corners and the join, divided by usable width, gives the number of strips. Multiply by strip width — 2½″ for a standard double-fold — and divide by 36 for yards. A throw at 60″ × 72″ has a 264″ perimeter, needs 7 strips, and takes ½ yard.

Bias binding, needed if you have curved edges, takes roughly 20% more and is calculated differently — from the area of the square you cut it from rather than from strips.

A rough sanity check

If you want a number before you have a design: a two-fabric throw quilt usually lands around 2–3 yards of each top fabric, 4 yards of backing and ½ yard of binding. A queen roughly doubles the top fabric and needs 8–9 yards of standard backing. Use it to decide whether a bundle is worth buying — then get the real number before you cut.

Questions