How to Calculate Backing Fabric

Once I get to the backing, I'm at the point where I'm ready to be done. Typically I go for the 108inch wide backing so I don't have to mess with seams. But there are times when I find the perfect backing fabric, that doesn't come in a wide backing and I need to do some quilt math.

WOF = 42 inches

Seam Allowance = 1/2 inch

How much backing fabric do you need?

1. Measure the length and width of your quilt top

   1. Example: Quilt top measures 74x85

2. Add at least 8 inches to the length and width. This is essential for the longarming process.

   1. Example: Quilt top measures 74x85 I'll need to add 8 inches to the length and width. So my new measurement is 82x93

3. Determine how many sections you will need.

   1. If your quilt is <34 inches, you will only need one section, no seams needed.

      1. Why 34? Because WOF is 42 and we need 8 inches extra for longarm.

   2. If your quilt is >35 <76, you will need to cut two sections which will require one seam

   3. If your quit is >77, then you will need at least three sections which will require two seams.

4. Multiply the length times the number of sections you will need and divide by 36 (a yard of fabric is 36 inches).

   1. Example: ((93x3)=279)/36=7.75

      1. Note: for a quilt top length of 85 inches, I will ned 3 sections.

5. Cut the fabric and sew sections together using a half inch seam allowance. Press seams open.

6. Trim the backing piece to the measurement in step 2.

What about directional fabric?

Depending on the direction of the fabric, will determine if you would prefer a horizontal seam or a vertical seam. In step 4 of the above, you would use the width measurement for a horizontal seam or the length measurement for a vertical seam.

That is all there is to it. It's just a little bit of quilt math and a couple a seams to get a beautifully pieced quilt backing.

Below is a backing I used in a recent quilt. Its from Tula Pink and is a 108 wide back. This was great to work with because it's not directional so it didn't matter how I loaded it on the longarm. When deciding on a quilt backing fabric, I keep direction in mind.