.ecg-calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
background: #fff;
padding: 20px;
border-radius: 8px;
box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}
.ecg-calc-header {
text-align: center;
margin-bottom: 25px;
color: #2c3e50;
}
.ecg-form-group {
margin-bottom: 20px;
}
.ecg-form-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #34495e;
}
.ecg-form-group input, .ecg-form-group select {
width: 100%;
padding: 12px;
border: 1px solid #bdc3c7;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.ecg-form-group .help-text {
font-size: 12px;
color: #7f8c8d;
margin-top: 4px;
}
.ecg-btn {
background-color: #e74c3c;
color: white;
padding: 15px 30px;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 18px;
font-weight: bold;
width: 100%;
transition: background 0.3s;
}
.ecg-btn:hover {
background-color: #c0392b;
}
.ecg-results {
margin-top: 30px;
background-color: #f8f9fa;
padding: 20px;
border-radius: 4px;
border-left: 5px solid #e74c3c;
display: none;
}
.ecg-result-item {
display: flex;
justify-content: space-between;
align-items: center;
padding: 10px 0;
border-bottom: 1px solid #e0e0e0;
}
.ecg-result-item:last-child {
border-bottom: none;
}
.ecg-result-label {
color: #555;
font-weight: 500;
}
.ecg-result-value {
font-size: 24px;
font-weight: 700;
color: #2c3e50;
}
.ecg-bpm-main {
text-align: center;
font-size: 48px;
color: #e74c3c;
font-weight: 800;
margin: 10px 0;
}
.ecg-article {
margin-top: 40px;
line-height: 1.6;
color: #333;
}
.ecg-article h2 {
color: #2c3e50;
margin-top: 30px;
}
.ecg-article ul {
padding-left: 20px;
}
.ecg-article li {
margin-bottom: 10px;
}
.warning-box {
background-color: #fff3cd;
color: #856404;
padding: 10px;
border-radius: 4px;
margin-top: 20px;
font-size: 0.9em;
}
function updateEcgLabels() {
var method = document.getElementById('calculation_method').value;
var label = document.getElementById('input_label_dynamic');
var input = document.getElementById('ecg_input_value');
if (method === 'small_squares') {
label.innerText = 'Number of Small Squares between R waves';
input.placeholder = 'e.g., 20';
} else if (method === 'large_squares') {
label.innerText = 'Number of Large Squares between R waves';
input.placeholder = 'e.g., 4';
} else if (method === 'rr_seconds') {
label.innerText = 'R-R Interval Duration (Seconds)';
input.placeholder = 'e.g., 0.8';
} else if (method === 'rr_milliseconds') {
label.innerText = 'R-R Interval Duration (Milliseconds)';
input.placeholder = 'e.g., 800';
}
}
function calculateECG() {
// Get inputs
var speed = parseFloat(document.getElementById('paper_speed').value);
var method = document.getElementById('calculation_method').value;
var inputVal = parseFloat(document.getElementById('ecg_input_value').value);
// Elements for output
var resultContainer = document.getElementById('ecg_result_container');
var bpmDisplay = document.getElementById('main_bpm_display');
var classDisplay = document.getElementById('hr_classification');
var rrDisplay = document.getElementById('rr_interval_display');
// Validation
if (isNaN(inputVal) || inputVal <= 0) {
alert("Please enter a valid positive number.");
resultContainer.style.display = 'none';
return;
}
var heartRate = 0;
var rrIntervalMs = 0;
// Calculation Logic
if (method === 'small_squares') {
// Formula: Speed (mm/s) * 60 / (Input * Size of small square in mm)
// Small square is usually 1mm.
// Standard 25mm/s: 1500 / Small Squares
// 50mm/s: 3000 / Small Squares
if (speed === 25) {
heartRate = 1500 / inputVal;
rrIntervalMs = inputVal * 40; // 1 small square = 0.04s = 40ms at 25mm/s
} else {
heartRate = 3000 / inputVal;
rrIntervalMs = inputVal * 20; // 1 small square = 0.02s = 20ms at 50mm/s
}
} else if (method === 'large_squares') {
// Formula: Standard 25mm/s: 300 / Large Squares
// 50mm/s: 600 / Large Squares
if (speed === 25) {
heartRate = 300 / inputVal;
rrIntervalMs = inputVal * 200; // 1 large square = 0.20s = 200ms at 25mm/s
} else {
heartRate = 600 / inputVal;
rrIntervalMs = inputVal * 100; // 1 large square = 0.10s = 100ms at 50mm/s
}
} else if (method === 'rr_seconds') {
// HR = 60 / Seconds
heartRate = 60 / inputVal;
rrIntervalMs = inputVal * 1000;
} else if (method === 'rr_milliseconds') {
// HR = 60000 / Milliseconds
heartRate = 60000 / inputVal;
rrIntervalMs = inputVal;
}
// Classification Logic
var classification = "";
var roundedHR = Math.round(heartRate);
if (roundedHR = 60 && roundedHR 100) {
classification = "Tachycardia (Fast)";
classDisplay.style.color = "#e74c3c";
}
// Display Results
bpmDisplay.innerHTML = roundedHR + "
";
classDisplay.innerText = classification;
rrDisplay.innerText = Math.round(rrIntervalMs) + " ms";
resultContainer.style.display = 'block';
}
How to Calculate Heart Rate from an ECG
Determining the heart rate from an Electrocardiogram (ECG/EKG) strip is a fundamental skill for medical professionals. The method used often depends on the regularity of the heart rhythm and the precision required. This calculator employs the standard formulas used in clinical settings.
Understanding the Grid
ECG paper is standardized with a grid layout to allow for the measurement of time (horizontal axis) and voltage (vertical axis). At the standard paper speed of 25 mm/s:
- 1 Small Square (1mm) represents 0.04 seconds.
- 1 Large Square (5mm, comprising 5 small squares) represents 0.20 seconds.
- 5 Large Squares represent 1 second.
Method 1: The 1500 Rule (Most Precise)
This method is best for regular rhythms and offers the highest accuracy. It involves counting the number of small squares between two consecutive R waves (the R-R interval).
Formula: Heart Rate = 1500 / Number of Small Squares
Example: If there are 20 small squares between two R waves, the heart rate is 1500 ÷ 20 = 75 BPM.
Method 2: The 300 Rule (Quick Estimation)
This is a rapid method ideal for regular rhythms where you count the large squares between R waves. It is essentially a simplified version of the 1500 rule (1500 ÷ 5 = 300).
Formula: Heart Rate = 300 / Number of Large Squares
Sequence for estimation: Find an R wave on a thick line. The next thick lines represent 300, 150, 100, 75, 60, 50 BPM respectively.
Method 3: Time-Based (R-R Interval)
If you have measured the exact duration between beats in seconds or milliseconds, you can calculate the rate mathematically without counting squares manually.
Formula: Heart Rate = 60 / R-R Interval (in seconds)
Normal vs. Abnormal Heart Rates
For an average adult at rest:
- Normal Sinus Rhythm: 60 to 100 BPM.
- Bradycardia: Less than 60 BPM.
- Tachycardia: Greater than 100 BPM.
Note: If the rhythm is irregular (the distance between R waves varies), the "6-Second Strip Method" is preferred, where you count the number of QRS complexes in a 6-second strip and multiply by 10.