While a basketball may be inflated to a maximum of 9 psi, balls are generally inflated to a pressure of 8 psi. As a general rule, properly inflated balls dropped from a height of 72 inches bounce off the playing surface to a height of 49 to 54 inches.
Most manufacturers instruct users to inflate their balls from 7 to 9 psi. The exact pressure needed for play is affected by the playing surface, environmental temperature and external air pressure. For example, due to thinner air and less resistance, a ball inflated to exactly 8 psi at high elevations reaches a greater height than the same ball dropped from the same height at sea level. While under-inflated balls bounce low and erratically, over-inflated balls may leak.