Ball Size Guide


Please read all the information carefully before selecting a ball. A few minutes spent reading now might save you the time and money of having to return a wrong-sized ball later…and pay to have another shipped!

The general rule for choosing the correct exercise ball size for core (abs/low back) exercises is to have your knees and hips bent to 90 degrees (thighs parallel to floor) when sitting on the ball. This is the minimum ball size–some people prefer a larger ball, where hips are higher than knees. Don’t go by photos of models sitting on balls. Typically they sit on a ball much larger than they would train on as it photographs better.

Consider how you will use the ball and your body characteristics (see below). Also, keep in mind that if you are a novice exerciser and/or have poor balance, a larger ball will provide more stability and support, thus making exercising easier (muscles won’t work as hard).

To avoid being disappointed that your ball is smaller than you expected, test out the ball size before ordering. Most people underinflate a ball because it is so firm (like a rock) inflated to its maximum diameter. To see if a 55cm ball is right for you, place a mark on a wall about 20 inches high (16 in. for a 45cm ball), and squat next to it. Consider that you will sink down a few inches (depending on your weight and amount of inflation). This is approximately how tall the ball will be when sitting on it. Get a larger size if you don’t like this height!



Your Height Ball Size (max. height/diameter)

less than 5′ 0″ 45 cm (18 in.)

5′ 0″ to 5′ 5″ 55 cm (22 in.)  [purchase]

5′ 6″- 6′ 1″ 65 cm (26 in.)  [purchase]

6′ 2″ – 6′ 8″ 75 cm (30 in.)  [purchase]

6′ 9″ and up 85 cm (34 in.)

Note: Only the Fitness Ball is available in 45cm & 85cm sizes


  • have long legs for your height
  • have back problems
  • are using the ball for stretching, yoga, or as an office chair

An exercise ball is VERY firm at its maximum diameter. If in doubt, go with a larger ball (you don’t have to inflate it to the maximum diameter). This means getting a ball one size larger than the chart suggests if you are near the upper range.

Using an Exercise Ball as an Office Chair

If your desk height is 29-30 inches and you are of average height and weight, the 65cm ball is the preferred size. However, consideration must be given to the height of the chair seat you will be replacing — keeping in mind the ball will sink down when you sit on it. The amount of sinking depends on your weight and how much you inflate it. (The ball will be firmer, i.e. sink less, when inflated closer to its maximum diameter.) A general guideline is to get a ball with a max. diameter that is at least 4 inches greater than your chair height. If in doubt as to what size to get, check with others who use a ball as an office chair–some people prefer the 75cm so we can’t make any guarantees that the 65cm will be right for you.