A method and device for heart rate measurement uses a stream of signals containing ECG signals to select a reference QRS complex according to a set of predetermined criteria and obtain electrical signal characteristics of the reference QRS complex. A first QRS complex is detected from the stream of signals and characterized in relation to the reference QRS in the time domain such that the first QRS complex meets another set of predetermined criteria, and satisfies a level of similarity with the reference QRS complex. An instantaneous heart rate of a subject is evaluated based on the first and the reference QRS complexes when the first and the second QRS complexes are sufficiently similar.