ECG Heart Rate Calculator

How to calculate ECG Heart Rate?

ECG paper moves at a standard speed of 25 mm/s. This means one large grid box (5mm) equals 0.2 seconds and one small box (1mm) equals 0.04 seconds. Since there are 300 large boxes in one minute (60 seconds / 0.2), we use the number 300 as a constant for rate calculation.

Formula: HR = 300 / Large Boxes or 1500 / Small Boxes

Using the ECG calculator: an example

Suppose you are looking at an ECG rhythm strip where you count exactly 4 large boxes between two consecutive R-wave peaks (the R-R interval).

Step-by-step calculation:

1. Identify two consecutive R waves on the ECG strip.
2. Count the number of large boxes between them (4).
3. Divide 300 by 4 to find the heart rate (75 BPM).

Frequently Asked Questions

What is a normal resting heart rate?

For most healthy adults, a normal resting heart rate ranges from 60 to 100 beats per minute (BPM). Rates below 60 are considered bradycardia, and rates above 100 are considered tachycardia.

When should I use the 6-second method?

The 6-second method is the most accurate way to calculate heart rate when the heart rhythm is irregular (like in Atrial Fibrillation). You count the number of QRS complexes in a 6-second interval and multiply by 10.

What does a large box represent on ECG paper?

On standard ECG grid paper, one large box is 5mm by 5mm. Horizontally, it represents 0.2 seconds of time. Vertically, it represents 0.5 millivolts (mV) of electrical amplitude.