Electrocardiograms (ECG or EKG) are vital tools for assessing the electrical activity of the heart. One of the most common calculations performed using an ECG is determining the heart rate. This tells us how many times the heart is beating per minute. There are several methods to calculate heart rate from an ECG strip, depending on the regularity of the rhythm and the available information on the strip.
Methods for Calculating ECG Heart Rate:
Using the R-R Interval (Most Accurate for Regular Rhythms):
The R-R interval is the time between two consecutive R waves on an ECG. The R wave represents ventricular depolarization, and measuring the time between them gives us the duration of one cardiac cycle.
If you measure the R-R interval in small boxes (each typically 0.04 seconds), the formula is: Heart Rate (bpm) = 1500 / Number of Small Boxes between R-R waves.
If you measure the R-R interval in large boxes (each typically 0.20 seconds, or 5 small boxes), the formula is: Heart Rate (bpm) = 300 / Number of Large Boxes between R-R waves.
The 6-Second Strip Method (For Irregular Rhythms):
This method involves counting the number of QRS complexes (the wide, spiky part of the ECG wave representing ventricular depolarization) within a 6-second strip and multiplying by 10. This is an estimation and is best used for irregular rhythms where precise R-R interval measurement is unreliable.
This calculator primarily uses the R-R interval method, allowing you to input the interval in seconds, or derive it from the number of large or small boxes for convenience. A normal resting heart rate for adults is typically between 60 and 100 beats per minute (bpm). Rates below 60 bpm are considered bradycardia, and rates above 100 bpm are considered tachycardia.