Planning the Quilt Back
You can piece leftover fabrics from the quilt top or from an entirely different quilt project. This is especially charming when you are making a reproduction or historical quilt.
Like batting, the backing needs to be larger than the quilt top. This allows for the fabric that is taken up during the quilting and for stabilization when using a quilting frame. Always add 6" to both the length and width measurements so you have an extra 3" all around.
Don’t forget to trim off the selvedge edge of your fabric. Leaving it on will cause your quilt backing to pucker or curve inward in the finished quilt.
If your quilt top is wider or longer than the width or length of your backing fabric, you will need to piece the backing. If seams are necessary, you need to decide whether your want them to be horizontal or vertical on the back of the quilt.
If your quilt is 40 to 60" wide, horizontal seams save on yardage. If your quilt is wider than 60", you may use one or two vertical seams. A quilt 81 to 120" requires a backing that is pieced with vertical seams.
The quilt top’s measurement determines how many pieces are in the backing. Standard calculations assume 42" of usable fabric can be cut from 44/45"-wide fabric. Some manufacturers offer 60"-, 90"-, or 108"-wide fabrics, but the color selection is limited.