.ecg-calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
color: #333;
line-height: 1.6;
}
.ecg-calc-box {
background: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.ecg-calc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 24px;
font-weight: 700;
}
.ecg-input-group {
margin-bottom: 20px;
background: #fff;
padding: 15px;
border-radius: 6px;
border: 1px solid #dee2e6;
}
.ecg-input-group h4 {
margin-top: 0;
margin-bottom: 10px;
color: #0056b3;
font-size: 16px;
}
.ecg-label {
display: block;
margin-bottom: 8px;
font-weight: 600;
font-size: 14px;
}
.ecg-input {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.ecg-btn {
display: block;
width: 100%;
padding: 15px;
background-color: #d32f2f;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background 0.3s;
margin-top: 20px;
}
.ecg-btn:hover {
background-color: #b71c1c;
}
.ecg-result {
margin-top: 25px;
padding: 20px;
background-color: #e8f5e9;
border: 1px solid #c8e6c9;
border-radius: 6px;
display: none;
}
.ecg-result h3 {
margin-top: 0;
color: #2e7d32;
text-align: center;
}
.ecg-metric {
display: flex;
justify-content: space-between;
border-bottom: 1px solid #a5d6a7;
padding: 10px 0;
}
.ecg-metric:last-child {
border-bottom: none;
}
.ecg-val {
font-weight: bold;
color: #1b5e20;
}
.ecg-article {
background: #fff;
padding: 20px;
}
.ecg-article h2 {
color: #2c3e50;
border-bottom: 2px solid #d32f2f;
padding-bottom: 10px;
margin-top: 30px;
}
.ecg-article h3 {
color: #d32f2f;
margin-top: 25px;
}
.ecg-article ul {
padding-left: 20px;
}
.ecg-article li {
margin-bottom: 10px;
}
.note {
font-size: 0.9em;
color: #666;
font-style: italic;
}
.grid-visual {
background-color: #ffebee;
border: 1px solid #ffcdd2;
color: #c62828;
padding: 10px;
font-size: 0.9em;
margin-top: 5px;
}
function calculateECG() {
// Get inputs
var smallSq = document.getElementById("smallSquares").value;
var largeSq = document.getElementById("largeSquares").value;
var qrs = document.getElementById("qrsCount").value;
var shortRR = document.getElementById("shortestRR").value;
var longRR = document.getElementById("longestRR").value;
var heartRate = 0;
var methodUsed = "";
var classification = "";
var rhythmStatus = "Not Checked";
// Logic to determine which method to use
// Priority: Small Squares (most accurate) > Large Squares > QRS Count
if (smallSq && parseFloat(smallSq) > 0) {
heartRate = 1500 / parseFloat(smallSq);
methodUsed = "1500 Method (Small Squares)";
} else if (largeSq && parseFloat(largeSq) > 0) {
heartRate = 300 / parseFloat(largeSq);
methodUsed = "300 Method (Large Squares)";
} else if (qrs && parseFloat(qrs) > 0) {
heartRate = parseFloat(qrs) * 10;
methodUsed = "6-Second Strip Method";
} else {
alert("Please enter a value in one of the sections to calculate the rate.");
return;
}
// Round Heart Rate
heartRate = Math.round(heartRate);
// Classification
if (heartRate < 60) {
classification = "Bradycardia ( 100) {
classification = "Tachycardia (>100 bpm)";
} else {
classification = "Normal Sinus Rate (60-100 bpm)";
}
// Rhythm Check
if (shortRR && longRR) {
var s = parseFloat(shortRR);
var l = parseFloat(longRR);
// Standard variance allowance is roughly 0.12s (3 small squares) or sometimes 0.16s
// We will use < 4 small squares difference as the threshold for Regular
var diff = Math.abs(l – s);
if (diff < 4) {
rhythmStatus = "Regular (Variation < 0.16s)";
} else {
rhythmStatus = "Irregular (Variation ≥ 0.16s)";
}
}
// Output Results
document.getElementById("resBPM").innerHTML = heartRate + " BPM";
document.getElementById("resMethod").innerHTML = methodUsed;
document.getElementById("resClass").innerHTML = classification;
document.getElementById("resRhythm").innerHTML = rhythmStatus;
document.getElementById("ecgResult").style.display = "block";
}
How to Calculate Rate and Rhythm on ECG
Interpreting an Electrocardiogram (ECG/EKG) begins with two fundamental steps: determining the heart rate and identifying the rhythm. Accurate calculation is vital for diagnosing arrhythmias, bradycardia, and tachycardia. This guide explains the standard paper speed settings (25mm/s) and the three primary mathematical methods used in clinical practice.
1. The 1500 Method (Small Squares)
The 1500 method is the most precise way to calculate heart rate for regular rhythms. Standard ECG paper moves at 25mm per second. Since there are 1500 small squares in one minute (25mm/s × 60s = 1500mm), you can determine the Beats Per Minute (BPM) by counting the small squares between two consecutive R waves.
Formula: Heart Rate = 1500 ÷ Number of Small Squares between R-R
Example: If there are 20 small squares between two R waves: 1500 ÷ 20 = 75 BPM.
2. The 300 Method (Large Squares)
The 300 method is a quick estimation tool, ideal for rapid assessment of regular rhythms. ECG paper is divided into large squares (5mm), each containing 5 small squares. There are 300 large squares in one minute (300 × 0.20s = 60s).
Formula: Heart Rate = 300 ÷ Number of Large Squares between R-R
Example: If there are 4 large squares between R waves: 300 ÷ 4 = 75 BPM. The sequence to memorize for large square lines is: 300, 150, 100, 75, 60, 50.
3. The 6-Second Method (Irregular Rhythms)
When the heart rhythm is irregular (e.g., Atrial Fibrillation), the R-R intervals vary, making the 1500 and 300 methods inaccurate. The 6-second method provides an average rate.
Procedure:
- Identify a 6-second strip on the ECG paper (30 large squares).
- Count the number of QRS complexes (R waves) within this strip.
- Multiply the count by 10 to get the rate for 60 seconds.
Example: If you count 8 QRS complexes in a 6-second strip: 8 × 10 = 80 BPM.
Determining Rhythm Regularity
Rhythm is defined as the pattern of heartbeats. To determine if a rhythm is regular:
- Use calipers or a piece of paper to mark the distance between two consecutive R waves (the R-R interval).
- Move the calipers to the next pair of R waves.
- If the distance remains constant across the strip, the rhythm is Regular.
- If the distance varies by more than 0.12 seconds (3 small squares), the rhythm is Irregular.
Normal vs. Abnormal Findings
Once you have calculated the rate and checked the rhythm, compare your results against standard clinical ranges:
- Normal Sinus Rhythm: 60–100 BPM, Regular rhythm.
- Sinus Bradycardia: < 60 BPM, Regular rhythm.
- Sinus Tachycardia: > 100 BPM, Regular rhythm.
- Arrhythmia: Irregular rhythm, rate may vary.