How to Calculate Quilt Backing

Start with the finished quilt width and length, then add extra backing on every side. A common planning default is 4 inches per side, though longarm quilters may request a specific amount.

The basic formula is: required backing width = quilt width + extra × 2, and required backing length = quilt length + extra × 2. Divide the required width by usable fabric width to estimate the number of panels.

After you know the panel count, multiply the panel count by the required backing length, divide by 36, and round up to buy fabric in yards.