A method for calibrating a rotary encoder, in particular an incremental encoder, of an electrical machine, wherein the encoder has a number of reference marks and outputs a sine track and a cosine track. The electrical machine can be regulated to a specific speed, an angle of the electrical machine is determined with the aid of the sine track and/or the cosine track, from this an angular progression over time is ascertained, an oscillation in the angular progression over time with a frequency of substantially one integral multiple of the product of the specific speed and the number of reference marks is ascertained, and from this a correction factor the sine track and/or the cosine track is derived, wherein the amplitude of the oscillation is less than or equal to a limiting value. The invention further relates to an encoder evaluation and an electric motor having a rotary encoder.