.ecg-calc-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 0;
border: 1px solid #e0e0e0;
border-radius: 8px;
background: #ffffff;
box-shadow: 0 4px 12px rgba(0,0,0,0.05);
}
.ecg-calc-header {
background: #ef5350; /* Medical Red */
color: white;
padding: 20px;
border-radius: 8px 8px 0 0;
text-align: center;
}
.ecg-calc-header h3 {
margin: 0;
font-size: 24px;
font-weight: 600;
}
.ecg-calc-body {
padding: 25px;
display: flex;
flex-wrap: wrap;
gap: 30px;
}
.ecg-method-section {
flex: 1 1 300px;
padding: 20px;
border: 1px solid #eee;
border-radius: 6px;
background-color: #fafafa;
}
.ecg-method-title {
font-weight: 700;
color: #333;
margin-bottom: 10px;
font-size: 16px;
border-bottom: 2px solid #ef5350;
display: inline-block;
padding-bottom: 5px;
}
.form-group {
margin-bottom: 15px;
}
.form-group label {
display: block;
font-weight: 500;
margin-bottom: 5px;
color: #555;
font-size: 14px;
}
.form-group input {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.form-group .help-text {
font-size: 12px;
color: #888;
margin-top: 4px;
}
.calc-btn {
width: 100%;
padding: 12px;
background-color: #263238;
color: white;
border: none;
border-radius: 4px;
font-size: 15px;
cursor: pointer;
font-weight: 600;
transition: background 0.2s;
}
.calc-btn:hover {
background-color: #37474f;
}
.result-section {
width: 100%;
margin-top: 20px;
padding: 20px;
background-color: #e3f2fd;
border: 1px solid #bbdefb;
border-radius: 6px;
text-align: center;
display: none;
}
.result-value {
font-size: 36px;
font-weight: bold;
color: #1976d2;
margin: 10px 0;
}
.result-status {
font-size: 18px;
font-weight: 600;
}
.status-normal { color: #2e7d32; }
.status-warning { color: #f57f17; }
.status-danger { color: #c62828; }
.article-container {
max-width: 800px;
margin: 40px auto;
font-family: inherit;
line-height: 1.6;
color: #333;
}
.article-container h2 {
color: #2c3e50;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
margin-top: 30px;
}
.article-container h3 {
color: #455a64;
margin-top: 25px;
}
.article-container p {
margin-bottom: 15px;
}
.article-container ul {
margin-bottom: 20px;
padding-left: 20px;
}
.article-container li {
margin-bottom: 8px;
}
.highlight-box {
background: #f9f9f9;
border-left: 4px solid #ef5350;
padding: 15px;
margin: 20px 0;
}
function getInterpretation(bpm) {
if (bpm < 60) {
return '
';
}
}
function displayResult(bpm, method) {
var roundedBPM = Math.round(bpm);
var resultDiv = document.getElementById("resultContainer");
var bpmDiv = document.getElementById("bpmResult");
var interpDiv = document.getElementById("interpretation");
var methodDiv = document.getElementById("methodUsed");
bpmDiv.innerHTML = roundedBPM + "
";
interpDiv.innerHTML = getInterpretation(roundedBPM);
methodDiv.innerText = "Calculated using: " + method;
resultDiv.style.display = "block";
// Scroll to result
resultDiv.scrollIntoView({behavior: "smooth"});
}
function calculateSmallSquares() {
var squares = document.getElementById("smallSquaresInput").value;
if (squares === "" || squares <= 0) {
alert("Please enter a valid number of small squares (greater than 0).");
return;
}
var bpm = 1500 / parseFloat(squares);
displayResult(bpm, "1500 Method (Small Squares)");
}
function calculateLargeSquares() {
var squares = document.getElementById("largeSquaresInput").value;
if (squares === "" || squares <= 0) {
alert("Please enter a valid number of large squares (greater than 0).");
return;
}
var bpm = 300 / parseFloat(squares);
displayResult(bpm, "300 Method (Large Squares)");
}
function calculateSixSecond() {
var count = document.getElementById("rWavesInput").value;
if (count === "" || count < 0) {
alert("Please enter a valid number of R-waves.");
return;
}
var bpm = parseFloat(count) * 10;
displayResult(bpm, "6-Second Strip Method");
}
How to Calculate Heart Rate in an ECG Graph
Electrocardiograms (ECGs) are fundamental tools in cardiology used to assess the electrical activity of the heart. One of the primary data points derived from an ECG is the heart rate (BPM). While modern ECG machines calculate this automatically, understanding how to calculate heart rate manually from the graph paper is a critical skill for medical professionals, especially when verifying machine data or analyzing rhythm strips manually.
Standard ECG paper moves at a speed of 25 mm per second. The paper is divided into a grid of small and large squares:
- Small Square: 1mm wide, represents 0.04 seconds.
- Large Square: 5mm wide (5 small squares), represents 0.20 seconds.
Method 1: The 1500 Method (Most Precise)
The 1500 method is the most accurate technique for calculating heart rate, provided the heart rhythm is regular (the distance between R waves is consistent).
Formula: Heart Rate = 1500 ÷ Number of Small Squares between two R waves.
Why 1500? Because there are 1,500 small squares in one minute (25mm/sec × 60 sec = 1500 mm/min).
Example: If there are 20 small squares between two consecutive R waves:
1500 ÷ 20 = 75 BPM.
Method 2: The 300 Method (Quick Estimate)
The 300 method, also known as the sequence method, is a faster variation of the 1500 method. It uses large squares instead of small squares. It is excellent for quick bedside assessments of regular rhythms.
Formula: Heart Rate = 300 ÷ Number of Large Squares between two R waves.
Why 300? Because there are 300 large squares in one minute (1500 small squares ÷ 5).
Example: If there are 4 large squares between R waves:
300 ÷ 4 = 75 BPM.
The sequence for rapid memorization is: 300, 150, 100, 75, 60, 50. If the interval is 1 large square, the rate is 300; if 2, the rate is 150, and so on.
Method 3: The 6-Second Method (Irregular Rhythms)
When the heart rhythm is irregular (such as in Atrial Fibrillation), the distances between R waves vary, making the 1500 and 300 methods inaccurate. In these cases, the 6-second method provides an average heart rate.
Formula: Count the number of R waves (QRS complexes) in a 6-second strip and multiply by 10.
A 6-second strip consists of 30 large squares. To use this method, identify a 6-second section on the graph paper, count the number of R peaks appearing in that window, and multiply that count by 10 to estimate the rate for 60 seconds.
Example: You count 8 R waves in a 30-large-square strip:
8 × 10 = 80 BPM.
Clinical Interpretation of Results
Once you have calculated the heart rate, compare it against standard clinical ranges:
- Normal Sinus Rhythm: 60 to 100 BPM.
- Bradycardia: Less than 60 BPM (Slow heart rate).
- Tachycardia: Greater than 100 BPM (Fast heart rate).
Always consider the patient's clinical context. For example, a heart rate of 50 BPM may be normal for a well-trained athlete (sinus bradycardia) but concerning for an elderly patient with syncope.