Quilt Back Math

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Quilt backing is the fabric used on the back of a quilt. It’s the bottom layer of the quilt sandwich: top, batting, backing. The important thing to remember about the backing is that it is always the biggest part of the sandwich.

Once you’ve finished a your beautiful top and are ready to start putting quilting stitches in, it’s time to build your sandwich. Pick a batting and decide on your quilt backing.

There a few things to consider when creating a quilt back.

Quilt Width: How wide is your quilt?

Measure your quilt top and record the dimensions.

Add 6″- 12″ to the width and the height.

If you’re quilting the project on your domestic machine, 3″ extra on each side is plenty, so add 6″ to the width and 6″ to the height.

width (+6″) x height (+6″)

65″ x 75″ = 71″ x 81″

If you are sending your quilt to another quilter to quilt, ask them for their preferences. Some longarm quilters request up to an extra 6″ per side. For the best results, it is best to check with your quilter and provide quilt backs in the sizes they request.

This measurement is the final size you need for your quilt back.

108″ fabrics or 42″ fabrics?

Depending on the size of backing you need, determine if you’d prefer to use a wide backing fabric 108″ – 120″ or a traditional 40″ to 42″ fabric.

The advantage of a wide backing fabrics, is that you don’t have to piece it. You simply purchase the amount of fabric you need according to your measurements.

Using 40″-42″ Width Fabrics

(All measurements for working with the width of fabric are given here without the selvages. Please remove all selvages from the fabric before quilting.)

If one of your quilt back measurements are 42″ or less use the other measurement to determine how much fabric to buy.

For example:

Quilt Backing Size: 42″ x 60″

60″ – 36″ (1 yard) = 24″ (2/3 yard)  So you will need 1 2/3 yards.

If both of your quilt back measurements are larger than 42″ you will need to piece your backing into one big piece to match your measurements.

There are two common ways to piece a back:

Horizontal Assembly

Sew two or more cuts of fabric together so the height of the quilt back is created from the width of fabrics.

Let’s say the fabric without selvages and seam allowances is 40″ wide. Using the horizontal method, each stack represents 40″. So two stacks is 80″ and three is 120″. Use the height quilt backing measurement to determine how many stacks you need.

Next, multiply the number of stacks by the width needed to determine yardage.

2 x 60″= 120″ You need 120″ of fabric to make your backing. Convert 120″ to yardage by dividing by 36″ and you get 3 1/3 yards.

The horizontal piecing method saves fabric for quilts up to 60″. For larger quilts, the vertical method is the most economical.

Vertical Assembly

Sew two or more cuts of fabric together so the width of the quilt back is created from the width of fabrics used.

Using the vertical method, each side-by-side stack represents 40″. So two stacks is 80″ and three is 120″. Use the width quilt backing measurement to determine how many stacks you need.

Next, multiply the number of stacks by the height needed to determine yardage.

2 x 70″= 140″ You need 140″ of fabric to make your backing. Convert 140″ to yardage by dividing by 36″ and you get 3 yards and 32″ which rounds up to 4 yards.

Below is an example with two vertical seams using the same yardage we just figured. This may preferred to having a center seam. To do this, cut one of the lengths in half and sew to each side of the center cut.

For quilts 81″ and wider, you’ll need to three stacks or more.

Tips:

  • Cut off all selvage edges.
  • Use a 1/2″ seam allowance for a more secure seam.
  • Press to seams to one side.
  • When buying extra 40″ – 42″ fabric on sale for backing, remember a queen quilt usually takes 9 yards.
  • When buying 108″ wide backing on sale, 3 yards equals 108″ giving you an 108″ square.
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Carolyn Eng

As a longarmer, I prefer to put the selvage of the backing at the top and bottom of the quilt frame. Some fabric has more stretch selvage-to-selvage than lengthwise so I can maintain the tension better, when I roll the quilt, to prevent ‘bagging’. Also I like to pin the quilt on into the selvage. When the backing is sewn in pieces, I try to maintained that orientation in the pieces, otherwise some parts will bag more than others. I also prefer not to have big seam running top to bottom because the seam is tighter than the fabric and… Read more »