The circumference of a sphere is equal to the distance around a plane that passes through its center point, called a great circle. Since the two-dimensional slice of the sphere is a circle, the formula to find the circumference of a sphere is the same as the formula for a circle. C = 2πr The circumference of a sphere is equal to 2 times π times the sphere’s radius r. If you want to calculate the surface area of the sphere, use the formula: SA = 4πr Where SA is the surface area and r is the radius of the sphere.