PI

The PI function returns the approximate value of π (pi), the ratio of a circle’s circumference to its diameter.

PI()

Notes

The PI function does not have any arguments. However, you must include the parentheses.
The PI function is accurate to 15 decimal places.

Examples
=PI() returns approximately 3.14159265358979. =SIN(PI()/2) returns 1, the sine of π/2 radians or 90 degrees.

Examples

=PI() returns approximately 3.14159265358979.

=SIN(PI()/2) returns 1, the sine of π/2 radians or 90 degrees.