Basketball manufacturers measure the ball in circumference. A men's league basketball measures 29.5 inches, while a women's ball measures an inch less, coming in at 28.5 inches. But the basketball manufacturing process is not exact. The NBA allows for a margin of error, accepting balls that measure up to 29.875 inches. The NBA also allows a range of air pressures inside the ball, using balls inflated from 7.5 to 8.5 pounds of pressure. The air pressure may affect the weight of the ball, but you can generally count on a 22-ounce mens ball and a 20-ounce women's basketball.