What is the formula for calculating heart rate using small boxes on an ECG?

The formula for calculating heart rate using small boxes on an ECG is derived from the standard ECG paper, which is typically marked with a grid of small boxes. Each small box represents a specific duration of time, specifically 0.04 seconds. To find the heart rate, one needs to determine how many small boxes are present between two successive R waves (the peaks of the QRS complex, which indicate heartbeats).

By dividing 1500 by the number of small boxes between R waves, you can calculate the heart rate in beats per minute (bpm). This is because there are 1500 small boxes in one minute (60 seconds divided by 0.04 seconds per box equals 1500). Thus, if you count the number of small boxes between two consecutive R waves, using the formula 1500 divided by that number yields the heart rate in beats per minute.

This method is particularly useful for calculating heart rate in cases of regular rhythms, providing a quick and efficient way to assess heart rate directly from the ECG reading.