Most patterns call for 2 1/2" but I find this too wide for my taste.
I use 2 1/4" strips, then use a 3/8" seam to sew it to the quilt. When I turn it, it fits perfectly.
BTW, I machine sew all my bindings, so I sew them to the back of the quilt, then turn them to the front and topstitch in place.