## Purpose

## Return value

## Arguments

## Syntax

## 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: πr^{2}. With radius in cell A1, the same formula in Excel with the PI() function is:

```
=PI()*A1^2
```

### 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 wumbo.net for a more detailed explanation of key math concepts and formulas.