What size of Swiss Ball Should I Get?

Swiss Ball Size Guide

Sizes based upon height are approximate. If you are in between (for instance, you stand between 5′ 5″ and 5′ 6″ tall) you could opt to go either way. Consider your other body characteristics and how you plan to use the ball.

If you are 5′ 5″ and weigh 240 pounds, you probably ought to go with a 65 cm ball. On the other hand, if you are 5′ 5″, but have very short legs, you might prefer a 55 cm ball. Similarly, if you intend to exercise while standing or lying on your back, the smaller ball would work better.

Still undecided?  When in doubt, it is safer to choose the larger size. You always have the option of inflating the ball less. Five foot five using a 65 cm ball? No sweat, just fit the exercise ball using the 90 degree rule in sitting. An under-inflated ball will not be as firm, but it will function just fine.