# Circumference of a circle

=2*PI()*A1

To calculate the circumference of a circle, you can use the PI function. In the example shown, the formula in C5, copied down, is:

=PI()*B5^2

which calculates the circumference of a circle with the radius given in column B.

In geometry, the circumference of a circle with radius (r) is defined by the following formula: =2πr` `

The Greek letter π ("pi") represents the ratio of the circumference of a circle to its diameter. In Excel, π is represented in a formula with the PI function, which returns the number 3.14159265358979, accurate to 15 digits.

=PI() // returns 3.14159265358979

Therefore, the formula to calculate the circumference of a circle with a radius of 3 is:

=2*PI()*3 // returns 18.85

And the formula to calculate circumference based on the radius values in column B, is:

=2*PI()*B5

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