Conversion Center

Radian (rad) is the SI unit of angle. It is a derived SI unit, defined as m⋅m^-1, which means that angles are dimensionless. One radian is the angle at the center of a circle that cuts off an arc of length equal to the radius. Since the circumference equals 2 π times the radius, one radian equals 1/(2 π) of the circle, or approximately 57.296^o.