Each long arm quilter has their own policy concerning this... It is best to contact the quilter you plan to send your quilt to and ask how much they require. I always ask for 5" all the way around ( so, a 70" X 80" quilt would require a backing at least 80" X 90"). But, I have had plenty of quilts come in with less (and a few with a lot more) different frames, leaders and the way a person does things all factor in So, only your quilter can tell you what you need