How to use the Excel RADIANS function

Summary

The Excel RADIANS function converts degrees to radians. For example, =RADIANS(180) returns 3.1415 or the value of π (pi).

Purpose

Converts degrees into radians

Return value

Radians

Syntax

=RADIANS (angle)

Arguments

angle - Angle in degrees to convert to radians.

Usage notes

The RADIANS function takes an angle in degrees and converts it to radians. Radians measure angles using the radius of a circle. For example, to convert a 45 degree angle to radians the formula is:

=RADIANS(45) // Returns 0.785 or π/4

Explanation

Radians are a unit of measure for circles

A radian is equal to the amount of rotation required to travel one radius along the circumference of the circle, as seen in the image above. A full-rotation or 360° in radians is equal to the value of 2π. A half-rotation or 180° in radians is equal to the value of geometric constant π (pi).

= RADIANS(360) =2*PI() // A full rotation is 6.283...

= RADIANS(180) =PI() // A half rotation is 3.141...

Notes

To convert radians to degrees, see the DEGREES function.
A full-rotation (360°) in radians is equal to 6.283 or 2π
A half-rotation (180°) in radians is equal to 3.142 or π (pi).

Related functions

Excel DEGREES Function

The Excel DEGREES function converts angles (expressed in radians) to degrees. For example, the formula =DEGREES(PI()) returns 180.

Excel PI Function

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 the circle such as the area of a circle.