As noted previously, the 9 1/4 yards is 45" fabric is pieced to fit your quilt. If you buy specific backing material (90-110" wide), then you would need 3 yards and the back would all be one piece. Connecting threads has some dreamy backing fabric, Joann's carries about 10 fabrics in the wide widths for quilt backing, and some LQS either have it, or can order if. Any way you go depends on what look you want, or what you can afford.