.ecg-calculator-container {
max-width: 600px;
margin: 20px auto;
padding: 25px;
background-color: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
font-family: Arial, sans-serif;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.ecg-calculator-container h3 {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
}
.ecg-form-group {
margin-bottom: 15px;
}
.ecg-form-group label {
display: block;
margin-bottom: 8px;
font-weight: bold;
color: #495057;
}
.ecg-form-group select, .ecg-form-group input {
width: 100%;
padding: 10px;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.ecg-btn {
width: 100%;
padding: 12px;
background-color: #d9534f;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
cursor: pointer;
transition: background-color 0.3s;
margin-top: 10px;
}
.ecg-btn:hover {
background-color: #c9302c;
}
.ecg-result {
margin-top: 20px;
padding: 15px;
background-color: #fff;
border-left: 5px solid #d9534f;
display: none;
}
.ecg-result h4 {
margin: 0 0 10px;
color: #333;
}
.ecg-result .bpm-value {
font-size: 32px;
font-weight: bold;
color: #d9534f;
}
.ecg-info {
font-size: 14px;
color: #666;
margin-top: 5px;
}
.ecg-content {
max-width: 800px;
margin: 40px auto;
font-family: Arial, sans-serif;
line-height: 1.6;
color: #333;
}
.ecg-content h2 {
color: #2c3e50;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
margin-top: 30px;
}
.ecg-content h3 {
color: #d9534f;
margin-top: 25px;
}
.ecg-content ul {
background: #f9f9f9;
padding: 20px 40px;
border-radius: 5px;
}
.ecg-content li {
margin-bottom: 10px;
}
function updateInputLabel() {
var method = document.getElementById("calcMethod").value;
var label = document.getElementById("inputLabel");
var input = document.getElementById("inputValue");
if (method === "small") {
label.innerText = "Number of Small Squares (1mm) between R-R";
input.placeholder = "e.g., 20";
} else if (method === "large") {
label.innerText = "Number of Large Squares (5mm) between R-R";
input.placeholder = "e.g., 4";
} else {
label.innerText = "Time Duration between R-R (Seconds)";
input.placeholder = "e.g., 0.8";
}
}
function calculateECG() {
var method = document.getElementById("calcMethod").value;
var value = parseFloat(document.getElementById("inputValue").value);
var speed = parseInt(document.getElementById("paperSpeed").value);
var resultDiv = document.getElementById("result");
var bpmOutput = document.getElementById("bpmOutput");
var rhythmType = document.getElementById("rhythmType");
if (isNaN(value) || value <= 0) {
alert("Please enter a valid positive number for the R-R interval.");
resultDiv.style.display = "none";
return;
}
var heartRate = 0;
// Logic based on Method
// Standard speed is 25mm/s.
// 1 minute = 60 seconds = 1500mm.
// Formula: HR = (Speed * 60) / Distance_mm
if (method === "small") {
// Value is number of small squares (1mm each)
// If speed 25mm/s: HR = 1500 / value
// If speed 50mm/s: HR = 3000 / value
heartRate = (speed * 60) / value;
} else if (method === "large") {
// Value is number of large squares (5mm each)
// Distance in mm = value * 5
// If speed 25mm/s: HR = 1500 / (value * 5) = 300 / value
// If speed 50mm/s: HR = 3000 / (value * 5) = 600 / value
heartRate = (speed * 60) / (value * 5);
} else if (method === "time") {
// Value is seconds
// HR = 60 / seconds
heartRate = 60 / value;
}
// Round to nearest integer
heartRate = Math.round(heartRate);
// Interpretation
var interpretation = "";
if (heartRate 100) {
interpretation = "Indicates Tachycardia (Fast Heart Rate)";
} else {
interpretation = "Normal Resting Heart Rate Range";
}
bpmOutput.innerText = heartRate;
rhythmType.innerText = interpretation;
resultDiv.style.display = "block";
}
How Is Heart Rate Calculated from ECG?
Calculating heart rate from an electrocardiogram (ECG or EKG) is a fundamental skill for medical professionals and students. While modern ECG machines provide automated analysis, manual verification is crucial for accuracy, especially when artifacts or arrhythmias are present. The calculation relies on measuring the distance between consecutive R waves (the R-R interval) on the ECG grid paper.
Understanding ECG Grid Paper
Before calculating, it is essential to understand the dimensions of standard ECG paper. The paper typically moves at a speed of 25 mm/second.
- Small Square (1mm): Represents 0.04 seconds in duration.
- Large Square (5mm): Consists of 5 small squares and represents 0.20 seconds in duration.
- One Minute: Contains 1,500 small squares or 300 large squares (at 25 mm/s).
Method 1: The 1500 Method (Small Square Method)
This is the most precise method for calculating heart rate for regular rhythms. It is particularly useful when the R-R interval does not fall exactly on the heavy lines of the large squares.
Formula: Heart Rate = 1500 / Number of Small Squares between R waves
Example: If there are 20 small squares between two consecutive R waves:
1500 ÷ 20 = 75 BPM.
Method 2: The 300 Method (Large Square Method)
This method provides a quick estimate and is ideal for regular rhythms where the R waves fall close to the large square grid lines. It relies on the memory sequence: 300, 150, 100, 75, 60, 50.
Formula: Heart Rate = 300 / Number of Large Squares between R waves
Example: If there are 4 large squares between two R waves:
300 ÷ 4 = 75 BPM.
Method 3: The Time Interval Method
If you have digital calipers or a precise time measurement provided by monitoring software, you can calculate the rate using the actual time in seconds.
Formula: Heart Rate = 60 / R-R Interval (in seconds)
Example: If the time between beats is 0.8 seconds:
60 ÷ 0.8 = 75 BPM.
Adjusting for Paper Speed
While 25 mm/sec is the global standard, some settings (like pediatric cardiology or stress testing) may use 50 mm/sec to spread out the waveform. If the paper speed is 50 mm/sec, the math changes:
- 1500 Method becomes the 3000 Method: HR = 3000 / Small Squares.
- 300 Method becomes the 600 Method: HR = 600 / Large Squares.
Interpreting the Results
Once you have calculated the heart rate, interpretation typically follows these guidelines for adults:
- Normal Sinus Rhythm: 60 to 100 BPM.
- Sinus Bradycardia: Less than 60 BPM.
- Sinus Tachycardia: Greater than 100 BPM.