# Radius of a Sphere Calculator

Want to calculate the radius of a sphere? Cool, try this calculator.

This radius of a sphere calculator will figure out the radius of any sphere given the diameter, the circumference, the surface area, or the volume of the sphere.

### Terminology

• "Sphere" - A three dimensional object contained by a surface that has all points at the same distance from the center. Basically, it's something that has a perfectly round ball shape.

• "Surface Area" - The total area occupied by the surface of a three dimensional object. It is expressed in square units of measurement, for example square feet, square meters, square inches, square yards, etc.

• "Volume" - The amount of space occupied by a three dimensional object. It is expressed in cubic units of measurement, for example cubic feet, cubic meters, cubic inches, cubic yards, etc.

• "Circumference" - If you a cut a sphere in half, the circumference would be the distance around the outside edge of the cut surface.

• "Diameter" - The distance of a straight line that extends from any point on the surface of the sphere to the surface point directly opposite, while passing through the center of the sphere.

• "Radius" - The distance of a straight line that extends from the center of the sphere to any point on the surface of the sphere.

### Calculating the Radius of a Sphere Using Diameter

If you know the diameter of a sphere, you can calculate the radius based on the following formula. This one's easy, the radius is always half of the diameter:

r = d / 2

where

d = Diameter

### Calculating the Radius of a Sphere Using Circumference

If you know the circumference of a sphere, you can calculate the radius based on the following formula:

r = C / 2 ϖ

where

ϖ = Pi = 3.14159265...
C = Circumference

### Calculating the Radius of a Sphere Using Surface Area

If you know the surface area of a sphere, you can calculate the radius based on the following formula:

where

A = Surface Area
ϖ = Pi = 3.14159265...