The Excel PI function returns the value of the geometric constant π (pi). The value represents a half-rotation in the radian angle system. The constant appears in many formulas relating the circle, such as the area of a circle.


Get the value of π

Return value 





Usage notes 

The PI function returns the value of π (pi) accurate to 15 digits. The value of π represents a half-turn in radians and appears in many formulas relating to the circle. The PI function takes no arguments:

=PI() // returns 3.14159265358979

Circumference of a circle

The constant π appears in many math formulas relating to the circle. The formula for the circumference of a circle is 2πr. Given a radius of 3, the same formula in Excel is:

=2*PI()*3 // circumference of circle, r=3

Area of a circle

The area enclosed by a circle with radius (r) is defined by the following formula: πr2. With radius in cell A1, the same formula in Excel with the PI() function is:


Radians to degrees

To convert an angle measured in radians in terms of π, the DEGREES function can be used to get the corresponding angle in degrees:

=DEGREES(PI()) // Returns 180°
=DEGREES(2*PI()) // Returns 360°

See for a more detailed explanation of key math concepts and formulas. 

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Dave Bruns

Hi - I'm Dave Bruns, and I run Exceljet with my wife, Lisa. Our goal is to help you work faster in Excel. We create short videos, and clear examples of formulas, functions, pivot tables, conditional formatting, and charts.