How to Calculate Heart Rate from Ecg Trace

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ECG Heart Rate Calculator

25 mm/sec (Standard) 50 mm/sec
Small Boxes (1mm) Large Boxes (5mm) Millimeters (mm)

Results:

Heart Rate: 0 BPM

Classification: N/A

function calculateECGHeartRate() { var paperSpeed = parseFloat(document.getElementById('paperSpeed').value); var measurementType = document.getElementById('measurementType').value; var interval = parseFloat(document.getElementById('rrInterval').value); var resultDiv = document.getElementById('ecgResult'); var bpmValue = document.getElementById('bpmValue'); var classificationValue = document.getElementById('classificationValue'); var mathLogic = document.getElementById('mathLogic'); if (isNaN(interval) || interval <= 0) { alert("Please enter a valid positive number for the R-R interval."); return; } var hr = 0; var logicText = ""; if (measurementType === "small") { // Formula: (Speed * 60) / (Interval * 1mm) // At 25mm/s: 1500 / small boxes hr = (paperSpeed * 60) / (interval * 1); logicText = "Calculation: (" + paperSpeed + "mm/s * 60 seconds) / " + interval + " small boxes."; } else if (measurementType === "large") { // Formula: (Speed * 60) / (Interval * 5mm) // At 25mm/s: 300 / large boxes hr = (paperSpeed * 60) / (interval * 5); logicText = "Calculation: (" + paperSpeed + "mm/s * 60 seconds) / (" + interval + " large boxes * 5mm)."; } else if (measurementType === "mm") { // Formula: (Speed * 60) / mm hr = (paperSpeed * 60) / interval; logicText = "Calculation: (" + paperSpeed + "mm/s * 60 seconds) / " + interval + " mm."; } var finalHR = Math.round(hr); bpmValue.innerHTML = finalHR; mathLogic.innerHTML = logicText; var classification = ""; var color = ""; if (finalHR = 60 && finalHR <= 100) { classification = "Normal Sinus Rhythm"; color = "#4caf50"; } else { classification = "Tachycardia (Fast Heart Rate)"; color = "#ff9800"; } classificationValue.innerHTML = classification; classificationValue.style.color = color; resultDiv.style.display = "block"; }

How to Calculate Heart Rate from an ECG Trace

Understanding how to manually calculate heart rate from an Electrocardiogram (ECG/EKG) strip is a fundamental skill for medical professionals and students. While many modern machines provide an automated interpretation, manual verification is critical, especially when dealing with irregular rhythms or artifacts.

1. The 300 Rule (Large Box Method)

This is the quickest method for regular rhythms. ECG paper is divided into large squares (5mm). Each large square represents 0.2 seconds at a standard paper speed of 25 mm/s. To calculate the heart rate:

  • Count the number of large boxes between two consecutive R-waves (the R-R interval).
  • Divide 300 by that number.
  • Example: If there are 4 large boxes between R-waves: 300 / 4 = 75 BPM.

2. The 1500 Rule (Small Box Method)

For a more precise calculation, use the small squares (1mm). Each small square represents 0.04 seconds. At a standard paper speed of 25 mm/s, there are 1,500 small boxes in one minute.

  • Count the number of small boxes between two consecutive R-waves.
  • Divide 1,500 by that number.
  • Example: If there are 20 small boxes: 1500 / 20 = 75 BPM.

3. The 6-Second Method (For Irregular Rhythms)

If the heart rhythm is irregular, the methods above may be inaccurate. Instead, use the 6-second strip method:

  • Count the number of R-waves (QRS complexes) within a 6-second interval (usually marked by small ticks at the top of the ECG paper).
  • Multiply the number of complexes by 10.
  • Example: If you count 8 complexes in 6 seconds: 8 x 10 = 80 BPM.

The Impact of Paper Speed

Standard ECG paper speed is 25 mm/sec. However, in some clinical settings (like pediatric cardiology), the speed might be increased to 50 mm/sec to spread out the complexes for better visibility. If the speed is doubled, the formulas change:

  • At 50 mm/s, use the 3000 Rule for small boxes.
  • At 50 mm/s, use the 600 Rule for large boxes.

Clinical Interpretations

Once you have calculated the heart rate, it is generally categorized as follows:

Rate (BPM) Classification
Below 60 Bradycardia
60 – 100 Normal Heart Rate
Above 100 Tachycardia

Note: This calculator is for educational purposes and should not replace professional medical diagnosis.

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