The Excel PI function simply returns the value of the mathematical constant π (pi), accurate to 15 digits (14 decimal places).
ie. the function returns the value 3.14159265358979
The Pi function takes no arguments and therefore has the simple format :
The spreadsheets below show an example of the Excel Pi function. The formula for the functions are shown in the spreadsheet on the left, and the results are shown in the spreadsheet on the right.
Formulas:

Results:

An overview of the mathematical constant, π is provided on the Wikipedia Pi page