Specifically designed for Atrial Fibrillation and irregular cardiac rhythms.
6 Seconds (Standard – 30 Large Boxes)
10 Seconds (Standard – 50 Large Boxes)
3 Seconds (15 Large Boxes)
How to Calculate Heart Rate in Irregular Rhythms
Calculating a heart rate from an ECG strip is straightforward when the rhythm is regular. However, when dealing with conditions like Atrial Fibrillation (AFib) or premature contractions, the distance between R-waves (the R-R interval) varies. This makes the "300 Method" or the "1500 Method" inaccurate.
To determine the heart rate for an irregular rhythm, medical professionals use the 6-Second Strip Method. Because an ECG paper records at a standard speed of 25mm/sec, we can measure a specific time interval and count how many heartbeats occurred within that window.
The 6-Second Rule Formula
The standard formula used in this calculator is:
Heart Rate (BPM) = (Number of QRS Complexes in 6 seconds) × 10
Step-by-Step Instructions:
Identify the strip length: Locate a 6-second section on your ECG printout. On standard ECG paper, 1 large box equals 0.2 seconds. Therefore, 30 large boxes equal 6 seconds.
Count the QRS: Count every QRS complex (the tall spikes) within those 30 large boxes.
Multiply: Take that number and multiply by 10 to get the beats per minute (BPM). If you are using a 10-second strip, multiply by 6.
Practical Examples
Example 1: Atrial Fibrillation
You have a 6-second ECG strip. You count 9 QRS complexes. Calculation: 9 x 10 = 90 BPM.
Example 2: Bradycardia with Irregularity
You have a 10-second ECG strip. You count 8 QRS complexes. Calculation: (8 / 10) * 60 = 48 BPM.
Why the "300 Method" Fails
The 300 method (300 divided by number of large boxes between R-waves) only looks at a single beat-to-beat interval. In an irregular rhythm, one interval might suggest 100 BPM while the next suggests 60 BPM. The timing method used here provides a mean heart rate, which is the clinical standard for irregular rhythms.
function calculateECGHeartRate() {
var qrs = document.getElementById("qrsCount").value;
var seconds = document.getElementById("stripLength").value;
var resultDiv = document.getElementById("ecg-result");
var textDiv = document.getElementById("resultText");
if (qrs === "" || qrs <= 0) {
alert("Please enter a valid number of QRS complexes.");
return;
}
// Calculation: (Count / Seconds) * 60 seconds per minute
var bpm = (parseFloat(qrs) / parseFloat(seconds)) * 60;
var roundedBpm = Math.round(bpm);
var status = "";
if (roundedBpm < 60) {
status = " (Bradycardia)";
} else if (roundedBpm > 100) {
status = " (Tachycardia)";
} else {
status = " (Normal Range)";
}
resultDiv.style.display = "block";
textDiv.innerHTML = "Estimated Mean Heart Rate:" +
"