An electrocardiogram (ECG or EKG) is a vital diagnostic tool used to assess the electrical activity of the heart. It records these electrical signals over a period of time, allowing healthcare professionals to detect abnormalities in heart rhythm and function. One of the most common calculations derived from an ECG is the heart rate.
There are several methods to calculate heart rate from an ECG tracing, depending on the information available and the paper speed of the ECG machine. Two common approaches are detailed below:
Method 1: Using the R-R Interval (Most Accurate for Regular Rhythms)
The R-R interval is the time duration between two consecutive R waves on an ECG, which represent the ventricular depolarization (contraction of the ventricles). For a regular heart rhythm, this interval is consistent. The formula is:
This calculator uses this method. You will need to measure the R-R interval in seconds from your ECG tracing. If you know the duration of one small box (typically 0.04 seconds) or one large box (typically 0.20 seconds) on the ECG paper and the paper speed (commonly 25 mm/sec), you can estimate the R-R interval.
Method 2: Using Large Boxes (Approximation for Regular Rhythms)
If the rhythm is regular, you can count the number of large boxes between two consecutive R waves and use the formula:
Heart Rate (beats per minute) = 300 / Number of Large Boxes between R-R
This calculator provides an option to input the R-R interval directly, which is the most precise way. If you prefer, you can also use the paper speed and large box duration to infer the R-R interval.
Why it Matters
A normal resting heart rate for adults is typically between 60 and 100 beats per minute. Rates outside this range (tachycardia – too fast, or bradycardia – too slow) can indicate various underlying medical conditions that require attention. This calculator helps you quickly get an estimate of your heart rate from an ECG.
Disclaimer: This calculator is for informational purposes only and should not be used for self-diagnosis or treatment. Always consult with a qualified healthcare professional for any health concerns.
function calculateHeartRate() {
var rrIntervalInput = document.getElementById("rrInterval");
var ecgPaperSpeedInput = document.getElementById("ecgPaperSpeed");
var largeBoxDurationInput = document.getElementById("largeBoxDuration");
var resultDiv = document.getElementById("result");
var rrInterval = parseFloat(rrIntervalInput.value);
var ecgPaperSpeed = parseFloat(ecgPaperSpeedInput.value);
var largeBoxDuration = parseFloat(largeBoxDurationInput.value);
var heartRate = NaN;
var errorMessage = "";
if (isNaN(rrInterval) || rrInterval <= 0) {
errorMessage = "Please enter a valid positive R-R interval in seconds.";
if (isNaN(rrIntervalInput.value) || rrIntervalInput.value === "") {
errorMessage = "Please enter the R-R interval in seconds.";
}
} else if (isNaN(ecgPaperSpeed) || ecgPaperSpeed <= 0) {
errorMessage = "Please enter a valid positive ECG paper speed in mm/sec.";
if (isNaN(ecgPaperSpeedInput.value) || ecgPaperSpeedInput.value === "") {
errorMessage = "Please enter the ECG paper speed in mm/sec.";
}
} else if (isNaN(largeBoxDuration) || largeBoxDuration <= 0) {
errorMessage = "Please enter a valid positive large box duration in seconds.";
if (isNaN(largeBoxDurationInput.value) || largeBoxDurationInput.value === "") {
errorMessage = "Please enter the large box duration in seconds.";
}
} else {
// Calculate heart rate directly if R-R interval is provided
heartRate = 60 / rrInterval;
// Optional: If R-R interval is not explicitly given but paper speed and large boxes are,
// you could potentially calculate it, but the direct R-R input is primary.
// For simplicity and clarity, we prioritize direct R-R input.
// If rrIntervalInput.value was empty, we would expect to calculate it from other inputs.
// However, the current design emphasizes direct R-R input.
}
if (!isNaN(heartRate)) {
resultDiv.innerHTML = "