Count all R-waves within the strip duration, including partial ones if applicable.
6 Seconds (Standard – 30 Large Boxes)
10 Seconds (Full Rhythm Strip)
3 Seconds (15 Large Boxes)
Standard rhythm strips are usually 6 seconds long (30 large squares at 25mm/s).
Ventricular Rate (Avg):— BPM
Calculating Heart Rate in Atrial Fibrillation
Calculating the heart rate from an electrocardiogram (ECG) during Atrial Fibrillation (AFib) presents a unique challenge due to the irregularly irregular nature of the rhythm. Standard calculation methods that rely on the distance between R-waves (such as the 300 or 1500 methods) are inaccurate because the R-R intervals vary significantly from beat to beat.
The 6-Second Method
The standard clinical method for estimating the ventricular rate in AFib is the 6-Second Method. This approach averages the heart rate over a longer period to account for the irregularity. The calculation logic used in the tool above follows this formula:
Formula: Heart Rate = (Number of R-Waves in 6 Seconds) × 10
If you are using a 10-second rhythm strip, you multiply the count by 6. This provides the average beats per minute (BPM).
Interpreting the Results
In the context of Atrial Fibrillation, the ventricular rate (heart rate) determines the urgency of treatment:
Controlled Ventricular Response: A resting heart rate between 60 and 100 BPM. This is generally the therapeutic goal for rate control strategies.
Rapid Ventricular Response (RVR): A heart rate greater than 100 BPM. In clinical settings, rates exceeding 110 BPM often require medication (such as beta-blockers or calcium channel blockers) to reduce symptoms and prevent tachycardia-induced cardiomyopathy.
Slow Ventricular Response (Bradycardia): A heart rate less than 60 BPM. This may indicate excessive rate-control medication or intrinsic conduction disease.
How to Count QRS Complexes
To use this calculator accurately:
Identify a 6-second strip on the ECG paper. At a standard paper speed of 25mm/s, this equals 30 large grid squares.
Count every QRS complex (the tall spikes representing ventricular contraction) that falls within these markers.
Enter the count into the calculator above.
Note: This calculator provides an estimate. Clinical decisions should always be made by a qualified healthcare professional reviewing the full 12-lead ECG.
function calculateAfibRate() {
// Get input values
var qrsInput = document.getElementById('qrs_count');
var durationInput = document.getElementById('strip_duration');
var resultSection = document.getElementById('results');
var bpmOutput = document.getElementById('bpm_output');
var statusOutput = document.getElementById('status_output');
var qrsCount = parseFloat(qrsInput.value);
var duration = parseFloat(durationInput.value);
// Validation
if (isNaN(qrsCount) || qrsCount < 0) {
alert("Please enter a valid number of QRS complexes.");
return;
}
// Calculation Logic: (QRS Count / Duration in Seconds) * 60 Seconds
// Example: 8 beats in 6 seconds = (8/6)*60 = 80 BPM
var heartRate = Math.round((qrsCount / duration) * 60);
// Determine Status based on AFib guidelines
var statusMessage = "";
var statusColor = "";
if (heartRate < 60) {
statusMessage = "Bradycardia (Slow Ventricular Response): The heart rate is lower than normal (= 60 && heartRate <= 100) {
statusMessage = "Controlled Ventricular Response: The rate is within the target resting range (60-100 BPM).";
} else if (heartRate > 100 && heartRate <= 110) {
statusMessage = "Tachycardia: The rate is elevated (> 100 BPM). Monitor closely.";
} else {
statusMessage = "Rapid Ventricular Response (RVR): The rate is uncontrolled (> 110 BPM). Rate control intervention may be indicated.";
}
// Display Results
bpmOutput.innerHTML = heartRate + " BPM";
statusOutput.innerHTML = statusMessage;
// Show result container
resultSection.style.display = "block";
}