# Circumference of a circle calculator

To calculate the circumference of a circle, you need to know the value of the circle’s radius (r), which is the distance from the center of the circle to its edge. Once you have the radius, you can use the following formula to calculate the circumference (C) of the circle:

C = 2πr

where π (pi) is a mathematical constant approximately equal to 3.14159.

### Here’s how to use a circumference of circle calculator:

1. Input the value of the radius (r) of the circle into the calculator.
2. Click on the “Calculate” button or press the “Enter” key.
3. The calculator will then display the circumference (C) of the circle, in units of length (such as meters, centimeters, or inches), based on the value of the radius you inputted.

For example, if the radius of a circle is 5 centimeters, the circumference of the circle would be:

C = 2πr C = 2 x 3.14159 x 5 C = 31.4159 cm

Therefore, the circumference of the circle with a radius of 5 centimeters is 31.4159 centimeters (rounded to four decimal places).