Calculate Heart Rate from Ecg Strip

ECG Heart Rate Calculator

Understanding ECG Heart Rate Calculation

Electrocardiogram (ECG or EKG) strips are a fundamental tool in diagnosing cardiac conditions. One of the most critical pieces of information derived from an ECG is the patient's heart rate. There are several methods to calculate heart rate from an ECG, each suitable for different scenarios and rhythms. This calculator provides two common methods: one using the R-R interval (the time between consecutive QRS complexes) and another using the duration of the ECG strip and the number of large boxes.

Method 1: Using the R-R Interval

This method is most accurate for regular rhythms. The R-R interval represents the time between two successive heartbeats. If you can accurately measure the time between two R waves (the tallest peak in the QRS complex), you can calculate the heart rate.

The formula is: Heart Rate (bpm) = 60 / R-R Interval (seconds)

For example, if the R-R interval is 0.80 seconds, the heart rate is 60 / 0.80 = 75 beats per minute (bpm).

Method 2: Using ECG Paper Speed and Large Boxes

ECG machines typically print on graph paper where each small box is 1mm wide and each large box is 5mm wide. The standard paper speed is 25 mm/sec. This means each large box represents 0.20 seconds (5mm / 25mm/sec).

For regular rhythms, you can count the number of large boxes between two consecutive R waves and use this to estimate the heart rate.

The formula is: Heart Rate (bpm) = 60 / (Number of Large Boxes * 0.20 seconds/box) Alternatively, if you know the paper speed: Heart Rate (bpm) = 60 / (Number of Large Boxes * (5mm / Paper Speed in mm/sec))

If there are 12 large boxes between R waves on paper running at 25 mm/sec, the heart rate is 60 / (12 * 0.20) = 60 / 2.40 = 25 bpm. This method is useful when the rhythm is regular and the R-R interval is not precisely measured.

Method 3: Using a Standard Strip Duration

If you have a known duration of the ECG strip recorded (e.g., 10 seconds) and can count the number of QRS complexes within that duration, you can calculate an average heart rate, which is particularly useful for irregular rhythms.

The formula is: Heart Rate (bpm) = Number of QRS Complexes * (60 / ECG Strip Duration in seconds)

For example, if you count 15 QRS complexes in a 10-second strip, the heart rate is 15 * (60 / 10) = 15 * 6 = 90 bpm.

function calculateHeartRate() { var rrInterval = parseFloat(document.getElementById("rrInterval").value); var stripDuration = parseFloat(document.getElementById("stripDuration").value); var ecgPaperSpeed = parseFloat(document.getElementById("ecgPaperSpeed").value); var largeBoxes = parseFloat(document.getElementById("largeBoxes").value); var resultDiv = document.getElementById("result"); resultDiv.innerHTML = ""; // Clear previous results var calculations = []; // Method 1: Using R-R Interval if (!isNaN(rrInterval) && rrInterval > 0) { var heartRateFromRR = 60 / rrInterval; calculations.push("

From R-R Interval: " + rrInterval.toFixed(2) + " seconds -> " + heartRateFromRR.toFixed(2) + " bpm

"); } // Method 2: Using Large Boxes and Paper Speed if (!isNaN(largeBoxes) && largeBoxes > 0 && !isNaN(ecgPaperSpeed) && ecgPaperSpeed > 0) { var secondsPerLargeBox = 5 / ecgPaperSpeed; var heartRateFromBoxes = 60 / (largeBoxes * secondsPerLargeBox); calculations.push("

From Large Boxes (" + largeBoxes + ") & Paper Speed (" + ecgPaperSpeed + " mm/sec): " + heartRateFromBoxes.toFixed(2) + " bpm

"); } // Method 3: Using Strip Duration if (!isNaN(stripDuration) && stripDuration > 0) { // This method requires counting QRS complexes which cannot be input directly. // We'll show a placeholder or guide the user. // For demonstration, let's assume we count QRS complexes. // In a real interactive calculator, you might have another input for QRS count. // For now, we'll explain its use. calculations.push("

From Strip Duration (" + stripDuration + " seconds): Count the number of QRS complexes in the " + stripDuration + "-second strip and multiply by (60 / " + stripDuration + "). (e.g., if 15 QRS complexes, rate is 15 * (60/10) = 90 bpm)

"); } if (calculations.length > 0) { resultDiv.innerHTML = "

Calculated Heart Rates:

" + calculations.join("") + "

"; } else { resultDiv.innerHTML = "Please enter valid numerical values for the selected calculation method(s)."; } }