Select the total time duration of the ECG tracing you are analyzing.
Count the number of R-waves (spikes) within the selected duration markers. Do not count incomplete cycles at the very edge.
Calculated Heart Rate:— BPM
Rhythm Interpretation:—
Multiplier Used:x10
function calculateBPM() {
// Get input elements
var qrsInput = document.getElementById('numQRSComplexes');
var stripSelect = document.getElementById('ecgTimeStrip');
var resultArea = document.getElementById('result-area');
var bpmDisplay = document.getElementById('bpmResult');
var badgeDisplay = document.getElementById('interpretationBadge');
var multiplierDisplay = document.getElementById('multiplierResult');
// Parse values
var rWaves = parseInt(qrsInput.value);
var duration = parseInt(stripSelect.value);
// Validation
if (isNaN(rWaves) || rWaves < 0) {
alert("Please enter a valid number of R-Waves.");
return;
}
// Calculation Logic: BPM = (Count / Seconds) * 60
// This handles 6s (x10), 10s (x6), etc. universally.
var multiplier = 60 / duration;
var bpm = Math.round(rWaves * multiplier);
// Interpretation Logic
var statusText = "";
var statusClass = "";
if (bpm = 60 && bpm <= 100) {
statusText = "Normal Resting Rate";
statusClass = "status-normal";
} else {
statusText = "Tachycardia (Fast)";
statusClass = "status-tachy";
}
// Update DOM
bpmDisplay.innerHTML = bpm + " BPM";
badgeDisplay.innerHTML = statusText;
badgeDisplay.className = "interpretation-badge " + statusClass;
multiplierDisplay.innerHTML = "x" + multiplier;
// Show results
resultArea.style.display = "block";
}
How to Calculate Heart Rate for Irregular Rhythms
Calculating the heart rate from an Electrocardiogram (ECG/EKG) is a fundamental skill for healthcare professionals. When the heart rhythm is regular, precise mathematical methods like the "300 Rule" (dividing 300 by the number of large squares between R-R intervals) work perfectly. However, these standard methods fail when the patient presents with an irregular rhythm, such as Atrial Fibrillation (AFib), Multifocal Atrial Tachycardia, or frequent ectopic beats.
Using the standard R-R interval method on an irregular strip will result in wildly fluctuating rate calculations depending on which two beats you measure. To get an accurate clinical picture, you must assess the average rate over a specific period. This is where the 6-Second Method comes in.
Clinical Note: An irregular rhythm is defined by R-R intervals that vary unpredictably. If the distance between the R-waves (the spikes) changes from beat to beat, you must use the method described below.
The 6-Second Method Explained
The 6-Second Method is the gold standard for estimating the mean heart rate of an irregular rhythm. It works on a simple principle: count the actual ventricular contractions (beats) that occur over 6 seconds and multiply by 10 to extrapolate to a full minute (60 seconds).
Step-by-Step Calculation Guide:
Step 1: Identify a 6-Second Strip. Most ECG paper contains markers (often small hash marks or triangles) at the top or bottom of the grid every 3 seconds. Identify two markers that are 6 seconds apart (usually 30 large boxes).
Step 2: Count the R-Waves. Count the number of complete QRS complexes (the tall spikes) that fall within this 6-second window.
Note: If a QRS complex falls exactly on the start line, count it. If it falls exactly on the end line, usually it is not counted, but consistency is key.
Step 3: Multiply by 10. Take the number of R-waves you counted and multiply it by 10. The result is the estimated Beats Per Minute (BPM).
Why Not Use the 300 or 1500 Rule?
The 300 rule (300 / number of large boxes) and the 1500 rule (1500 / number of small boxes) rely on the assumption that every cardiac cycle is identical in length. In conditions like Atrial Fibrillation:
One R-R interval might be 15 small boxes (Rate of 100).
The very next interval might be 25 small boxes (Rate of 60).
Calculating the rate based on just one of those intervals provides false data. The 6-second method averages these irregularities out, providing a "Mean Ventricular Rate" which is clinically actionable.
Interpretation of Results
Once you have calculated the rate, interpretation is based on standard adult resting heart rate parameters:
Bradycardia: Less than 60 BPM. In irregular rhythms, this is often "Slow AFib".
Normal: 60 to 100 BPM. This is considered "Controlled".
Tachycardia: Greater than 100 BPM. In AFib, this is often termed "AFib with Rapid Ventricular Response (RVR)".
Alternative: The 10-Second Method
While the 6-second method is the most common because the math (x10) is easy, some clinicians prefer a 10-second strip for greater accuracy. In this case, you count the R-waves over 10 seconds and multiply by 6. Our calculator above supports this method by changing the "ECG Strip Duration" dropdown.