1500 Method (Small Boxes between R-waves)
300 Method (Large Boxes between R-waves)
6-Second Strip Method (QRS complexes count)
Standard paper speed is 25mm/s.
function updateUnits() {
var method = document.getElementById("calculationMethod").value;
var label = document.getElementById("inputLabel");
var help = document.getElementById("methodHelp");
if (method === "small") {
label.innerHTML = "Number of Small Boxes (between two R-waves):";
help.innerHTML = "Formula: 1500 / boxes. Most accurate for regular rhythms.";
} else if (method === "large") {
label.innerHTML = "Number of Large Boxes (between two R-waves):";
help.innerHTML = "Formula: 300 / boxes. Faster for quick visual estimation.";
} else {
label.innerHTML = "Number of QRS Complexes (in a 6-second strip):";
help.innerHTML = "Formula: Count x 10. Best for irregular rhythms.";
}
}
function calculateECGHeartRate() {
var method = document.getElementById("calculationMethod").value;
var val = parseFloat(document.getElementById("boxCount").value);
var resultDiv = document.getElementById("ecgResult");
var bpmOutput = document.getElementById("bpmOutput");
var classOutput = document.getElementById("classificationOutput");
if (isNaN(val) || val <= 0) {
alert("Please enter a valid number greater than 0.");
return;
}
var bpm = 0;
if (method === "small") {
bpm = 1500 / val;
} else if (method === "large") {
bpm = 300 / val;
} else {
bpm = val * 10;
}
bpm = Math.round(bpm);
resultDiv.style.display = "block";
bpmOutput.innerHTML = bpm + " BPM";
if (bpm = 60 && bpm <= 100) {
classOutput.innerHTML = "Classification: Normal Heart Rate";
resultDiv.style.backgroundColor = "#d4edda";
resultDiv.style.color = "#155724";
resultDiv.style.border = "1px solid #c3e6cb";
} else {
classOutput.innerHTML = "Classification: Sinus Tachycardia";
resultDiv.style.backgroundColor = "#f8d7da";
resultDiv.style.color = "#721c24";
resultDiv.style.border = "1px solid #f5c6cb";
}
}
How do you calculate the heart rate on an ECG?
Calculating the heart rate (HR) from an Electrocardiogram (ECG or EKG) is a fundamental skill in clinical medicine. Standard ECG paper moves at a constant speed of 25 mm/second. This constant allows us to use specific mathematical shortcuts to determine the beats per minute (BPM).
1. The 1500 Method (Small Boxes)
This is the most accurate method for regular rhythms. Because there are 1,500 small boxes (1mm each) in one minute of ECG paper (25mm/s * 60s), you simply count the number of small boxes between two consecutive R-waves (the R-R interval).
Formula: 1,500 ÷ Number of Small Boxes = Heart Rate.
Example: If there are 20 small boxes between R-waves, 1500 / 20 = 75 BPM.
2. The 300 Method (Large Boxes)
A large box on an ECG contains 5 small boxes. Since 1500 / 5 = 300, we can use the large boxes for a faster estimation. This is often called the "Sequence Method."
Formula: 300 ÷ Number of Large Boxes = Heart Rate.
Example: If there are 4 large boxes between R-waves, 300 / 4 = 75 BPM. The standard sequence clinicians memorize is 300-1500-100-75-60-50 for consecutive large boxes.
3. The 6-Second Strip Method
This method is essential when the heart rhythm is irregular (like in Atrial Fibrillation), where R-R intervals vary. ECG paper usually has markers every 3 seconds. By taking a 6-second section (which equals 30 large boxes), you count how many QRS complexes occur and multiply by 10.
Formula: Number of QRS Complexes in 6 seconds × 10 = Heart Rate.
Example: If you count 8 QRS complexes in a 6-second strip, the heart rate is roughly 80 BPM.