Because the standard shower curtain is a 72-inch square, 5 yards of 45- or 54-inch wide fabric is needed to make one. More fabric may be necessary if it has a pattern that must be matched at the seam.
Shower curtains are typically hemmed on all four sides, so it is important to take measurements that account for this fact. An extra 16 inches for the top and bottom hems and an extra 8 inches for the side hems are required to end up with the final dimensions of 72 inches by 72 inches. The top end of the shower curtain can be finished with grommets or buttonholes, or it can be left untouched and attached to the shower rod with quilt hooks.