49"+6"=55". I would cut the width of the fabric at 55", which allows 3" of backing extending beyond the width of your quilt top edges( if quilting on your domestic machine.) Allow extra backing if you are bringing to a long arm quilter (4" around the perimeter of your quilt top 49"+8"=57")
Cut 2 pieces at 55" x 44". Join the 2 pieces along the 44" side with a half inch seam allowance to equal :55" w x 87"l . Trim the 87" to 62". You have a backing size of 62" l x 55" w for your quilt top of 56"l x 49"w.