Use this chart, to take the guesswork out of buying the correct size exercise ball.

5’7″ or shorter use a 55-centimeter ball.

5’7″ to 6’4″ use a 65-centimeter ball.

Taller than 6’4″ use a 75-centimeter ball.

Inflate the ball so that it’s firm. When you sit on it, your knees and hips should form a 90 degree angle.