A basketball should be inflated to between 7.5 and 8.5 psi (pounds per square inch). This gives the ball the proper amount of bounce on a hard surface. Lower psi leads to a weak bounce, while a higher psi would cause the ball to bounce too much.
Smaller air pumps are recommended for basketballs to help maintain the right inflation level. Use a pressure gauge to determine the correct psi. If you don’t have a pressure gauge, you can try the bounce test.
See More Basketball Trivia & Questions