Quilters ask me this question more often than any other: “How much backing do I need to buy if my quilt is size X?” There are a few ways to calculate this depending on the width of the fabric you’re buying. Most machine quilters will require at least 4” extra fabric in each direction for the quilting process; I will work that into my figures. I am also going off standard sizes for quilts: king, queen, full, etc. So, if your quilt falls outside those standards, recalculating would be wise ;)