### Calculating HEART RATE EASILY ON ECG :: -- Select a R wave on 1 thick line -- Select the next R wave complex . -- Measure the large squares amongst them. ... -- It's easier when remembered : 1 large square = 300 bpm, second large square = 150 bpm and so on ..... For more precise Heart rate :: count the number of small squares between two R - R complexes and divide it by 1500 Remember 1 large square = 0.2 seconds = 5 small squares