Question

How can you measure the circumference of ball?

Answer 1

Measure the circumference of the fitness ball. Fitness ball sizes are listed in diameter (the distance straight from one side of the sphere to the opposite side, passing through the center), not circumference. Divide the circumference by pi, or 3.14, to get the diameter.

Answer 2

Find the radius if you know the diameter. The radius is half the diameter, so use the formula r = D/2. ...
Find the radius if you know the circumference. Use the formula C/2π. ...
Calculate the radius if you know the volume of a sphere. Use the formula ((V/π)(3/4))1/3. ...
Find the radius from the surface area
hope it helps you...