Radian (rad)
A radian is the angle at the centre of a circle that cuts off an arc as long as the radius. A full turn is 2π radians, so π radians is 180° and 1 radian is about 57.2958°.
Symbol: rad
Quantity: plane angle
SI relation: rad is the coherent SI unit of angle.
Derivation: The SI unit of plane angle: the angle subtended at the centre of a circle by an arc equal in length to the radius (1 rad = 1 m/m).
Exact: yes, by definition
Typical uses
- Trigonometry and calculus (derivatives of sin and cos assume radians)
- Arc length s = rθ and angular speed
- SAT and ACT trigonometry questions
Convert radians to other units
| Conversion | 1 rad equals | Reverse |
|---|---|---|
| radian to degree | 57.29577951 ° | degree to radian |
| radian to gradian | 63.66197724 gon | gradian to radian |
| radian to revolution | 0.1591549431 rev | revolution to radian |
| radian to minute of arc | 3437.746771 ′ | minute of arc to radian |
| radian to second of arc | 206264.8062 ″ | second of arc to radian |
Open the Angle Converter to convert any value between all units.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 4 (radian) and Table 8 (non-SI units accepted for use with the SI).
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Radian (rad). Retrieved October 25, 2026, from https://scientificconverters.com/units/radian/
IEEE
Scientific Converters, "Radian (rad)," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/units/radian/