A method for calibrating a rotary encoder for measuring a rotary angle position of a machine shaft. The method includes rotating a machine shaft; measuring a start measuring point with a sensor unit; activating a timer module to measure a time value; measuring an intermediate measuring point with the sensor unit; storing the actual rotary angle position of the intermediate measuring point and the time value associated therewith; measuring an end measuring point with the sensor unit; recording a time value incremented by the timer module which reflects a runtime for a rotary motion of the start to the end measuring point; calculating at least one time-dependent reference rotary angle position; calculating a deviation between the actual rotary angle position measured and the at least one time-dependent reference rotary angle position calculated for at least one time value; and correcting an output signal from the rotary encoder via the deviation.