Because Pi = 180°, the general formula for degrees to radians is degrees * PI()/180. For example, to convert 45° to radians, the Excel formula would be 45*PI( )/180 which equals 0.7854 radians. More examples in the table below:
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.