Quilt Backing Calculator

How Much Backing Fabric Do You Need?

For a 60 × 80 in quilt top, buy 5 yd of 42 in quilting cotton, or 2 yd of wide backing. The calculator above works this out for any size.

The backing is the bottom layer of a quilt. It has to be bigger than the quilt top, so there’s spare fabric all the way around while you quilt; you trim it off at the end. The usual guide is 4 in extra on each side, which makes the backing 8 in wider and 8 in longer than the top. A 60 × 80 in top needs a 68 × 88 in backing. If a longarm quilter will finish your quilt, they often ask for 4–6 in on each side, so check with them first.

How to Use the Quilt Backing Calculator

1. Enter the width and length of your finished quilt top.
2. Choose the backing fabric width: 42 in · quilting for regular quilting cotton, 104 in · wide backing for wide backing, or Custom.
3. Check the extra backing on each side (4 in unless you change it).
4. Turn on Directional print if your fabric has an up and a down, such as trees or lettering.

The result shows how much to buy, how to cut and sew the pieces, and a drawing. A table compares vertical seams, horizontal seams and wide backing, and batting and binding have their own cards. The seam allowance, rounding step and backing price are under More options. The batting price is in the batting section, and the binding price is under Binding settings.

Vertical or Horizontal Seams?

Use whichever needs less fabric. That depends on your quilt’s size, so the calculator works out both and shows the cheaper one first.

Quilting cotton is narrower than most quilts, so you sew two or more pieces, called panels, together. With vertical seams, the panels run down the length of the quilt. With horizontal seams, they run across it. Here are two quilts on 42 in fabric:

For the 60 × 80 in top, two panels sewn side by side cover the 68 in width, so vertical seams need 5 yd. Turned the other way, two panels cover only 83 in of the 88 in length, so horizontal seams need a third panel and 5 3/4 yd.

For the smaller 50 × 70 in top, horizontal seams win: two panels of 58 in are enough, and you save 1 1/8 yd. A common rule of thumb says horizontal seams for quilts under about 60 in wide, but working out both is the only way to be sure.

Directional prints. If the print has an up and a down, horizontal seams would turn it on its side. Only vertical seams keep it upright, so the 50 × 70 in quilt would need 4 3/8 yd instead of 3 1/4 yd.

Why two 42 in widths don’t make 84 in

Each seam uses 1 in of fabric: a 1/2 in seam allowance from each piece. Two 42 in pieces sewn together measure 83 in, not 84 in: 1 in short of a backing that size. Some calculators divide the backing size by the fabric width and miss this, so their answer can come up short when a quilt is close to the limit.

Usable Width vs Labeled Width

Measure the width you can actually use. Fabric is labeled by its full width, but the selvages (the firm woven edges) are trimmed off before you sew panels together. Quilting cotton sold as 44/45 in is about 42 in once the selvages are off, and wide backing sold as 108 in is about 104 in. The calculator uses these usable widths. If yours is narrower, choose Custom and enter what you measured.

Wide Backing: One Piece, No Seams

Wide backing is fabric made for quilt backs, sold as 108 in wide (about 104 in usable). It covers most quilts in one piece, so there are no seams to sew.

Turn it the right way. For the 60 × 80 in top, lay it across the quilt so the fabric’s width runs down the 88 in length. Then you need only 68 in of it, so you buy 2 yd. Cutting it down the length instead would take 88 in, or 2 1/2 yd. The calculator always picks the shorter way and shows wide backing next to your other options, so you can compare the total price.

How Much Batting You Need

Batting is the soft middle layer. Give it the same extra as the backing: a 60 × 80 in top needs 68 × 88 in of batting.

Packaged batting comes in standard sizes. The smallest that covers 68 × 88 in is a Twin pack (72 × 90 in). Sizes vary by a few inches between brands, so these are typical sizes; check the package.

Batting also comes by the yard, cut from rolls about 90 to 120 in wide. A 68 × 88 in piece fits across a 90 in roll, so you need 68 in and buy 2 yd. If both sides of the batting you need are wider than the roll, lay two pieces side by side with the edges touching, not overlapping, and zigzag them together. The calculator works out how many pieces to cut.

How Much Fabric You Need for Binding

Binding is the narrow strip that wraps the quilt’s raw edges. You cut strips 2 1/2 in wide across the fabric and join them end to end with diagonal seams. For a 60 × 80 in quilt:

1. Add up the four sides: 280 in. Add 10 in for turning the corners and the final join: 290 in.
2. Each diagonal join uses about 2 1/2 in of length, so a strip cut from 42 in fabric gives about 39 1/2 in.
3. Divide 290 in by 39 1/2 in and round up: 8 strips. That’s 8 × 2 1/2 in = 20 in of fabric, so buy 5/8 yd.

If you forget the joins, you’d cut 7 strips, which only reach 276 1/2 in: not enough to go around.

Typical Quilt Sizes

Here’s what each common quilt size needs. Select a size to open it in the calculator above.

Worked out with the calculator’s starting settings: 4 in extra on each side, 1/2 in seams, quilting cotton sold as 44/45 in (about 42 in usable) or wide backing sold as 108 in (about 104 in usable), and 2 1/2 in binding strips, rounded up to 1/8 yd. Because the batting needs the same extra as the backing, a twin quilt needs a Queen batting pack, and full and queen quilts need a King pack.

Many patterns make full, queen and king quilts longer, about 108 in, so they tuck under the pillows. Enter your own size in the calculator above.

Cutting the quilt top too? The fabric calculator works out how much fabric you need for any set of pieces and draws the cutting layout.