Basketball was created out of winter-weather necessity in a western Massachusetts gym in 1891. Dr. James Naismith nailed peach baskets 10 feet high and tossed his students soccer balls, instructing them to score a basket. The game has evolved and so has the ball, enabling better grip for ball handling and dribbling.
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.