The present invention relates to device, system and method for counting the number of cycles of a periodic movement of a subject, e.g. for step counting of a person. To enable more precisely counting the number of cycles of a periodic movement of a subject based on discontinuous accelerometer data the proposed device comprises an input unit (21) for receiving discontinuous accelerometer data over time indicating movement of at least a body part of the subject, a classifier (22) for classifying the movement of the subject into one of several movement classes based on said discontinuous accelerometer data, each movement class being related to a different range of speed of a periodic movement, a storage (23) for storing a table including for each movement class a periodicity value per time unit, and a movement calculation unit (24) for calculating the number of cycles of the periodic movement of the subject per time unit, for a predetermined time or continuously over time by use of the periodicity of the movement class, into which the movement has been classified.