This calculator helps you determine your heart rate from an electrocardiogram (ECG) strip. Understanding your heart rate from an ECG is crucial for diagnosing various cardiac conditions.
function calculateHeartRateECG() {
var rrInterval = parseFloat(document.getElementById("rrInterval").value);
var paperSpeed = parseFloat(document.getElementById("paperSpeed").value);
var boxSize = parseFloat(document.getElementById("boxSize").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = "; // Clear previous results
if (isNaN(rrInterval) || rrInterval <= 0) {
resultDiv.innerHTML = 'Please enter a valid R-R interval (must be a positive number).';
return;
}
if (isNaN(paperSpeed) || paperSpeed <= 0) {
resultDiv.innerHTML = 'Please enter a valid ECG paper speed (must be a positive number).';
return;
}
if (isNaN(boxSize) || boxSize 0) {
heartRate = 60 / rrIntervalSeconds;
calculationMethod = `Using R-R interval in seconds (calculated from R-R interval in mm and paper speed)`;
}
// Method 2: Using number of large boxes (each large box is 5 small boxes)
// This is a common shortcut IF the strip is regular.
// The prompt specifically asks for 'boxSize' so we will use that.
// Assuming the input `boxSize` refers to the number of small boxes between R waves.
// Standard paper speed is 25 mm/sec, so 1500 small boxes = 1 minute.
// If paper speed is not 25 mm/sec, the 1500 constant needs adjustment.
// For simplicity and common ECG practice, we'll use the 1500 rule if boxSize is provided and valid.
// We'll prioritize the boxSize method if valid, as it's a very common quick estimate.
var alternativeHeartRate = 0;
if (!isNaN(boxSize) && boxSize > 0) {
// Standard method: 1500 small boxes per minute.
// Heart Rate = 1500 / number of small boxes between R-R
alternativeHeartRate = 1500 / boxSize;
heartRate = alternativeHeartRate; // Use this method as it's a direct box count
calculationMethod = `Using the 1500 rule (1500 / number of small boxes between R-R)`;
} else {
// If boxSize is not provided or invalid, fall back to the R-R interval in mm method.
// The code above already calculated heartRate using rrInterval and paperSpeed.
// No change needed, calculationMethod is already set.
}
resultDiv.innerHTML = `
Calculated Heart Rate: ${heartRate.toFixed(2)} bpm
Method used: ${calculationMethod}
Explanation:
The heart rate is calculated based on the time between consecutive R waves on the ECG strip (the R-R interval). A standard ECG paper moves at 25 mm/sec. Each small box on the grid is 1 mm, and each large box is 5 mm.
Method 1 (Using R-R Interval in mm):
First, we calculate the R-R interval in seconds by dividing the R-R interval in millimeters by the paper speed (in mm/sec).
Then, we multiply this interval by 60 to find the number of R-R intervals in one minute, which gives us the heart rate in beats per minute (bpm). Formula: Heart Rate = 60 / (R-R Interval in seconds).
Method 2 (The 1500 Rule – commonly used for regular rhythms):
This is a quick estimation method. It assumes a standard paper speed of 25 mm/sec.
Since there are 1500 small boxes in one minute (25 mm/sec * 60 sec/min = 1500 mm/min), you can divide 1500 by the number of small boxes between two consecutive R waves to get an approximate heart rate in bpm. Formula: Heart Rate = 1500 / Number of Small Boxes between R-R.
Note: The 1500 rule is most accurate for regular heart rhythms. For irregular rhythms, other methods like counting complexes over 6 seconds and multiplying by 10 are often preferred. This calculator assumes you are providing the R-R interval in mm or the number of small boxes between R-R waves for a regular rhythm.
`;
}
#ecgHeartRateCalculator {
font-family: sans-serif;
border: 1px solid #ccc;
padding: 20px;
border-radius: 8px;
max-width: 500px;
margin: 20px auto;
background-color: #f9f9f9;
}
#ecgHeartRateCalculator h2 {
text-align: center;
color: #333;
margin-bottom: 15px;
}
#ecgHeartRateCalculator p {
color: #555;
line-height: 1.6;
margin-bottom: 10px;
}
.calculator-inputs {
margin-bottom: 15px;
}
.input-group {
margin-bottom: 10px;
display: flex;
align-items: center;
}
.input-group label {
display: inline-block;
width: 150px;
margin-right: 10px;
font-weight: bold;
color: #444;
}
.input-group input[type="number"] {
padding: 8px;
border: 1px solid #ccc;
border-radius: 4px;
flex-grow: 1;
}
#ecgHeartRateCalculator button {
display: block;
width: 100%;
padding: 10px;
background-color: #4CAF50;
color: white;
border: none;
border-radius: 4px;
font-size: 16px;
cursor: pointer;
transition: background-color 0.3s ease;
}
#ecgHeartRateCalculator button:hover {
background-color: #45a049;
}
#result {
margin-top: 20px;
padding: 15px;
border: 1px dashed #ddd;
background-color: #fff;
border-radius: 4px;
}
#result p {
margin-bottom: 8px;
}
#result strong {
color: #333;
}
#result small {
color: #777;
font-style: italic;
}