2.25" for cotton batting, but 2.5 for polyester or high loft. I also leave an excess 1/8" of batting/ backing beyond the top whenever possible to keep binding full. I machine front & hand sew back. Just keep a small bit prepared binding pinned to your design wall or bulletin board near your machine. I do that with a sample of " majic binding", because l can never remember my cut measures for that,lol.