Hello all, Mary Ellen here.
A few years ago in my previous position as guild newsletter editor I shared a tip from John Flynn for calculating the size of a piece of fabric needed for your quilt back.
Some of you who have not been at this quilting thing since a coon’s age like the rest of us may not know who John Flynn is. Great big guy from Montana who does wonderful hand quilting, and comes up with quilting gadgets. Here’s a link to his humorous story of how he got started as a quilter.
Sometimes when our quilts are too wide for a standard width of 40-42 inches, but not really wide enough to justify buying the 108 inch wide backing or using two full widths of backing fabric, we try to make do with a pieced back. Of course, if you have enough fabric to piece together two lengths that are as long as our quilt, then you are good to go. But sometimes we don’t, or we don’t want the extra fabric wasted. (That’s the beginning of your personal war with scraps too big to throw away!) John’s method basically takes a standard width of fabric, slices it diagonally and then slides one of the triangles down a bit to sacrifice some length but gain some width. (The pictures at the site I’m linking to might help this make more sense.) John’s background as a civil engineer is a double edged sword here. It enables him to come up with the ideas and figure out the math needed, but it also means his explanation and formula are really mathy. TOO mathy, some might say. Now I myself have been accused of getting too “math teachery” (wink, wink) in my explanations sometimes, but I never have gone off the deep end like John does here! (Here is the link to John’s site–scroll down to diagonal backing–if you want to see the VERY MATHY formula! While you are there, read about his rag quilts-weed whacker style for a good chuckle. Only a man I say!) This morning I came across a website that will do the math in John’s formula for you. You just plug in your quilt’s dimensions and your available backing fabric dimensions, and it takes it from there. Go to this site if you want to give it a try!!
Either way this method (John’s way or the alternate website’s calculator) only is good if your quilt backing needed is 150% of the backing fabric’s width or less. Here’s a quote from John’s site with examples: “John’s method for diagonally piecing a quilt back, from one piece of fabric, is the most efficient way to make the back when the width of the quilt back is 1½ times, or less, than the width of the fabric you plan to use. For example, if the width of your back fabric is 44”, use John’s method whenever the width you want your back to be is 66” or less. If you are using fabric that is 60” wide, use John’s method whenever you want your quilt back to be 90” or less.” If you want a wider back you should just buy the two quilt lengths, but sew them together with a diagonal seam to make the quilting easier, and to have the “bump” of the seam less noticeable.
Here’s a pep talk from a fellow quilter on her experience with John’s method.