Circumference Calculator | Find the Distance Around a Circle

Circumference Calculator

Quickly calculate the circumference of any circle using its radius. Our tool also provides the diameter and area for a complete geometric overview.

Radius (r)

Enter the radius of the circle (e.g., 5, 12.5)

Please enter a valid positive number for the radius.

How it works

Quickly calculate the circumference of any circle using its radius. Our tool also provides the diameter and area for a complete geometric overview.

The Formula

Circumference (C) = 2πr
Diameter (d) = 2r
Area (A) = πr²

Worked Example

Example: Calculate Circumference for a Radius of 5 cm
If a circle has a radius (r) of 5 cm, its circumference (C) is calculated as C = 2 * π * 5 = 10π ≈ 31.4159 cm. The diameter would be 10 cm, and the area would be 25π ≈ 78.5398 cm².

Tips, Assumptions & Limitations

Remember that π (Pi) is approximately 3.14159.
If you have the diameter, simply divide it by 2 to get the radius before using the calculator.
The circumference is the distance around the circle, much like the perimeter of other shapes.

FAQ

The circumference of a circle is the total distance around its outer edge. It's similar to the perimeter of a polygon, but for a circular shape.

To calculate the circumference (C) using the radius (r), you use the formula C = 2πr, where π (Pi) is a mathematical constant approximately equal to 3.14159.

If you have the diameter (d) instead of the radius, you can use the formula C = πd. Remember that the diameter is simply twice the radius (d = 2r).

Pi (π) is a fundamental mathematical constant representing the ratio of a circle's circumference to its diameter. It's an irrational number, meaning its decimal representation goes on forever without repeating, commonly approximated as 3.14159.