I usually cut my binding to 2 1/2 inches. I fold it in half and press. Then I sew it to the front of the quilt with my walking foot. I would guess my seam allowance is around 3/8 or 1/2 inch??? I start sewing, maybe a few inches, then stop and check it, turning it to the back of the quilt to see if it will fold over enough to cover my stitching line. If it doesn't quite cover, I rip out the seam and start over, making it a little larger. I actually enjoy doing bindings. Maybe I should go into business and do bindings for all these fellow quilters who hate to do bindings!!! What do you think??? :)