Calculating Heart Rate

Calculating Heart Rate

This table can help make the sequencing method of determining heart rate more precise. After counting the number of boxes between the R waves, use the table shown at right to find the rate.

For example, if you count 20 small blocks or 4 large blocks, the rate would be 75 beats/min. To calculate the atrial rate, use the same method with P waves instead of R waves.

Rapid estimation

This rapid-rate calculation is also called the countdown method. Using the number of large boxes between R waves or P waves as a guide, you can rapidly estimate ventricular or atrial rates by memorizing the sequence “300, 150, 100, 75, 60, 50.”

Number of small blocks	Heart rate
5 (1 large block)	300
6	250
7	214
8	187
9	166
10 (2 large blocks)	150
11	136
12	125
13	115
14	107
15 (3 large blocks)	100
16	94
17	88
18	83
19	79
20 (4 large blocks)	75
21	71
22	68
23	65
24	63
25 (5 large blocks)	60
26	58
27	56
28	54
29	52
30 (6 large blocks)	50
31	48
32	47
33	45
34	44
35 (7 large blocks)	43
36	42
37	41
38	39
39	38
40 (8 large blocks)	37

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