Circumference Calculator

Radius
in
Diameter
in
Circumference
in
Area
in²

If you need to solve some geometry exercises, this circumference calculator might help you. It is a tool created to find the diameter, circumference and area of any circle. Continue reading to learn:

  • what is the definition of circumference,
  • how to find a circumference of a circle,
  • why is the ratio of circumference to diameter so important.

Definition of circumference

Circumference of a circle is the linear distance calculated along its edge. It is similar to perimeter of a geometric figure, but the term 'perimeter' is rather used to describe the property of polygons.

Formula for circumference

The following equation describes the relation between circumference and radius R of a circle:

C = 2πR

The constant π is approximately equal to 3.14159...

A similarly simple formula determines the relation between the area of a circle and its radius:

A = π * R^2

How to find the circumference of a circle

  1. Determine the radius of a circle. Let's assume it's equal to 14 cm.
  2. Substitute this value to the formula for circumference: C = 2*π*R = 2*π*14 = 87.9646 cm.
  3. You can also find the area of a circle: A = π * R^2 = π * 14^2 = 615.752 cm^2.
  4. Finally, you can find the diameter - it is simply two times the radius: D = 2*R = 2*14 = 28 cm.
  5. Use our circumference calculator to find the radius when given circumference or area of the circle.

If you wish to calculate the properties of a three-dimensional solid, such as a sphere, cylinder or cone, it's best to use our volume calculator.

Circumference to diameter

You probably noticed that since diameter is twice the radius, the proportion between circumference and diameter is equal to π:

C/D = 2πR / 2R = π

This proportion (circumference to diameter) is the definition of the constant pi. It is used in many areas, including physics and mathematics. For example, you can find it in the centrifugal force calculator.