The smallest basketballs are 5 to 6 inches in diameter and designed for toddlers and very young children. Larger basketballs come in standard sizes. The smallest size is size 1, which is 16 inches in circumference and designed for ages 2 to 4. The next size is size 3, which is 22 inches in circumference and suited for children ages 4 to 8. Size 4 balls are 25.5 inches are suitable for ages 5 to 8. Size 5 balls are 27.5 inches are suited for children ages 9 to 11. Size 6 balls are 28.5 inches and ideal for boys ages 12 to 14 and girls and women ages 12 and above. Size 7 balls are 29.5 inches and ideal for boys ages 15 and above.