http://www.flynnquilt.com/free-lessons.htm
John’s Formula for Joan’s Trick
DIAGONAL PIECED BACK
John’s method for diagonally piecing a quilt back, from one piece of fabric, is the most efficient way to make the back whenever the width of the quilt back in one and a half 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.
HOW DO YOU KNOW HOW
MUCH BACK FABRIC YOU NEED
It’s easy. John has calculated a simple formula to figure the yardage . Work through his example to get familiar with the formula and you will be able to figure out out how much back you need for any size quilt.
Example 1 Quilt top measures 48” x 60”.
You want your quilt back to be 51” x 66”. The desired length of the back goes in to the formula as LQ=66
John likes to use a ½” seam allowance, pressed open, for his quilt backs, so add 1” to the quilt back width. The desired back width goes in to the formula as WQ=51
For this example, the width of the fabric is 44”. This goes in to the formula as WF=44
Ready? Here is the formula!
LF = LQ + LQ (WQ-WF)
2WF-WQ
Solving for LF (yardage required)
LF = 66 + 66 x (51-44)
2x44 – 51
LF = 66 + 66x7
37
or (462 divided by 37) = 66, which is 12.5 inches + 66 inches, 78.5 inches, let’s just say 79”!
Copyright 2003 John Flynn
http://www.multi-patch.com/html/diagonal_backing_calculator.php
John’s Formula for Joan’s Trick
DIAGONAL PIECED BACK
John’s method for diagonally piecing a quilt back, from one piece of fabric, is the most efficient way to make the back whenever the width of the quilt back in one and a half 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.
HOW DO YOU KNOW HOW
MUCH BACK FABRIC YOU NEED
It’s easy. John has calculated a simple formula to figure the yardage . Work through his example to get familiar with the formula and you will be able to figure out out how much back you need for any size quilt.
Example 1 Quilt top measures 48” x 60”.
You want your quilt back to be 51” x 66”. The desired length of the back goes in to the formula as LQ=66
John likes to use a ½” seam allowance, pressed open, for his quilt backs, so add 1” to the quilt back width. The desired back width goes in to the formula as WQ=51
For this example, the width of the fabric is 44”. This goes in to the formula as WF=44
Ready? Here is the formula!
LF = LQ + LQ (WQ-WF)
2WF-WQ
Solving for LF (yardage required)
LF = 66 + 66 x (51-44)
2x44 – 51
LF = 66 + 66x7
37
or (462 divided by 37) = 66, which is 12.5 inches + 66 inches, 78.5 inches, let’s just say 79”!
Copyright 2003 John Flynn
http://www.multi-patch.com/html/diagonal_backing_calculator.php
