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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