The heart rate of ECG can be calculated by reading seconds method and formula calculation method. 1. Second reading method: The time represented by each small frame of ECG is 0.04s, and 5 small frames represent 1 second. Firstly, count the number of heart beats in 30 small frames (i.e. 6 seconds), and then multiply it by 10 to get the heartbeat of 1 minute, which is often used to calculate the heart rate in the case of arrhythmia. 2. Formula calculation method: R-wave is the highest wave on the ECG, and the time between neighboring R-waves is called RR interval. The RR interval is calculated by counting the number of squares between two R waves and substituting the RR interval into the formula: heart rate = 60/RR interval, which will result in the patient’s heart rate. By the formula calculation method, if the RR interval is exactly 3 bigrams, 4 bigrams and 5 bigrams apart, the corresponding heart rate is 100 beats/min, 75 beats/min and 60 beats/min respectively. Normal heart rate is 60-100 beats/min. If the calculated heart rate of ECG is not in the normal range, you should consult a doctor in time to avoid delaying your condition.