Calculate BPM using standard 25mm/s ECG paper measurements.
Number of Small Squares (1500 Method)
Number of Large Squares (300 Method)
R-R Interval (Seconds)
R-R Interval (Milliseconds)
0 BPM
Classification: —
How to Calculate Heart Rate from an ECG
Calculating the heart rate from an Electrocardiogram (ECG or EKG) strip is a fundamental skill for medical professionals. The method used depends on the regularity of the rhythm and the precision required. This calculator assumes a standard paper speed of 25 mm/second.
1. The 1500 Method (Small Squares)
This is the most precise method for calculating heart rate on regular rhythms.
How to use: Count the number of small squares (1 mm boxes) between two consecutive R waves (the R-R interval).
Formula: Heart Rate = 1500 / Number of Small Squares.
Why 1500? At a standard speed of 25 mm/s, there are 1500 small squares in one minute (25 mm/s × 60 s = 1500 mm).
Example: If there are 20 small squares between R waves, the heart rate is 1500 / 20 = 75 BPM.
2. The 300 Method (Large Squares)
This method is faster and useful for quick estimation on regular rhythms.
How to use: Count the number of large squares (5 mm boxes, defined by thicker grid lines) between two consecutive R waves.
Formula: Heart Rate = 300 / Number of Large Squares.
Why 300? There are 5 small squares in 1 large square. Therefore, 1500 / 5 = 300 large squares per minute.
Example: If there are 4 large squares between R waves, the heart rate is 300 / 4 = 75 BPM.
3. Using R-R Interval Time
Modern digital ECG machines often provide the exact time duration between beats in milliseconds (ms) or seconds.
Example: An R-R interval of 800ms (0.8s) results in a heart rate of 75 BPM.
Interpreting the Results
Normal Sinus Rhythm: 60 to 100 BPM. Sinus Bradycardia: Less than 60 BPM. Sinus Tachycardia: Greater than 100 BPM.
Note: This calculator is designed for educational purposes and initial estimation. Always verify automated calculations with clinical assessment. Irregular rhythms (like Atrial Fibrillation) require the "6-Second Method" (counting QRS complexes in a 6-second strip and multiplying by 10), which this tool does not currently calculate.
function updateEcgLabel() {
var method = document.getElementById('calculationMethod').value;
var label = document.getElementById('inputLabel');
var input = document.getElementById('ecgValue');
if (method === 'smallSquares') {
label.innerText = 'Number of Small Squares between R waves';
input.placeholder = 'e.g., 20';
} else if (method === 'largeSquares') {
label.innerText = 'Number of Large Squares between R waves';
input.placeholder = 'e.g., 4';
} else if (method === 'rrSeconds') {
label.innerText = 'R-R Interval duration (Seconds)';
input.placeholder = 'e.g., 0.8';
} else if (method === 'rrMilliseconds') {
label.innerText = 'R-R Interval duration (Milliseconds)';
input.placeholder = 'e.g., 800';
}
// Clear result when method changes to avoid confusion
document.getElementById('resultBox').style.display = 'none';
}
function calculateHeartRate() {
var method = document.getElementById('calculationMethod').value;
var val = parseFloat(document.getElementById('ecgValue').value);
var bpm = 0;
var resultBox = document.getElementById('resultBox');
var bpmDisplay = document.getElementById('bpmDisplay');
var classDisplay = document.getElementById('classificationDisplay');
// Validation
if (isNaN(val) || val <= 0) {
alert("Please enter a valid positive number.");
return;
}
// Calculation Logic
if (method === 'smallSquares') {
// Formula: 1500 / small squares
bpm = 1500 / val;
} else if (method === 'largeSquares') {
// Formula: 300 / large squares
bpm = 300 / val;
} else if (method === 'rrSeconds') {
// Formula: 60 / seconds
bpm = 60 / val;
} else if (method === 'rrMilliseconds') {
// Formula: 60000 / ms
bpm = 60000 / val;
}
// Round to nearest integer
var roundedBpm = Math.round(bpm);
// Determine Classification
var classification = "";
var statusClass = "";
if (roundedBpm = 60 && roundedBpm <= 100) {
classification = "Normal Resting Rate";
statusClass = "status-normal";
} else {
classification = "Tachycardia (Fast)";
statusClass = "status-tachy";
}
// Display Results
bpmDisplay.innerHTML = roundedBpm + " BPM";
classDisplay.innerHTML = "" + classification + "";
resultBox.style.display = 'block';
}