How do I choose which size Pilates ball to buy?

Like a pair of sneakers, you should definitely “try on” your exercise ball before you buy. There are a few tests you can do while shopping to ensure you purchase the perfect sphere. For starters, your feet should be flat on the floor (with your knees at a 90 degree angle) when you sit up straight on the ball. Generally, if you are 4-foot-11 to 5-foot-4, a 55cm ball will work for you; if you’re 5-foot-5 to 5-foot-11, get a 65cm ball; and if you’re 6-foot to 6-foot-7, try a 75cm ball.