2.Remove the plug from the ball and insert the nozzle of a hand pump or other inflation device.
3.Fill the ball with air until it appears fully inflated.
4.Remove the nozzle and re-insert the plug into the ball.
5.Measure the ball with a tape measure to determine the diameter. Reference the instructions on the owner's manual, or on the ball itself, to calculate the suggested diameter based on your height and weight. If the ball is not at the desired diameter, pump in more air or release air, then measure again.
6.Sit on the ball to confirm that the ball is properly inflated. Check to make sure your thighs are parallel to the floor, with your hips and knees in alignment.