Heart Rate in Ecg is Calculated by

ECG Heart Rate Calculator

Small Square Method (1500 Rule) Large Square Method (300 Rule) 6-Second Strip Method (Irregular Rhythm)

(1 small square = 0.04 seconds)

(1 large square = 0.20 seconds)

(Count the QRS peaks in a 30-large-square segment)

Calculated Heart Rate:

— BPM

document.getElementById('calcMethod').onchange = function() { var method = this.value; document.getElementById('smallSquareInput').style.display = method === 'small' ? 'block' : 'none'; document.getElementById('largeSquareInput').style.display = method === 'large' ? 'block' : 'none'; document.getElementById('sixSecondInput').style.display = method === 'sixSecond' ? 'block' : 'none'; }; function calculateECGHeartRate() { var method = document.getElementById('calcMethod').value; var hr = 0; var valid = false; if (method === 'small') { var smallSquares = parseFloat(document.getElementById('smallSquares').value); if (smallSquares > 0) { hr = 1500 / smallSquares; valid = true; } } else if (method === 'large') { var largeSquares = parseFloat(document.getElementById('largeSquares').value); if (largeSquares > 0) { hr = 300 / largeSquares; valid = true; } } else if (method === 'sixSecond') { var complexes = parseFloat(document.getElementById('rComplexes').value); if (complexes > 0) { hr = complexes * 10; valid = true; } } if (valid) { var resultDiv = document.getElementById('ecgResult'); var interpretationDiv = document.getElementById('ecgInterpretation'); var roundedHR = Math.round(hr); resultDiv.innerHTML = roundedHR + " BPM"; document.getElementById('ecgResultContainer').style.display = 'block'; if (roundedHR 100) { interpretationDiv.innerHTML = "Tachycardia (Fast)"; interpretationDiv.style.color = "#d32f2f"; } else { interpretationDiv.innerHTML = "Normal Sinus Rhythm"; interpretationDiv.style.color = "#2e7d32"; } } else { alert("Please enter a valid positive number."); } }

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How Heart Rate in ECG is Calculated

Understanding how heart rate in ECG is calculated is a fundamental skill for medical professionals and students. An Electrocardiogram (ECG) records the electrical activity of the heart over time, and because the paper speed is standardized, we can use the physical distance between heartbeats to determine the rate per minute.

1. The 1500 Rule (Small Square Method)

This is the most accurate method for regular rhythms. ECG paper moves at a standard speed of 25 mm/sec. This means that 1,500 small squares (1mm each) pass the needle in one minute. To find the heart rate, you count the number of small squares between two consecutive R waves (the R-R interval) and divide 1500 by that number.

Formula: 1500 / (Number of Small Squares between R-R)

2. The 300 Rule (Large Square Method)

A quicker method involves counting the large squares (5mm boxes). Since there are 300 large squares in a minute (1500 / 5), you can divide 300 by the number of large squares between R waves. This is excellent for rapid "bedside" assessments.

Formula: 300 / (Number of Large Squares between R-R)

3. The 6-Second Method

If the heart rhythm is irregular (like in Atrial Fibrillation), the R-R interval changes between every beat. In these cases, counting the squares between just two beats is inaccurate. Instead, you count the total number of R waves (QRS complexes) in a 6-second strip and multiply that number by 10.

Formula: Number of R waves in 6 seconds × 10

Example Calculations

Scenario	Measurement	Calculated Heart Rate
Regular Rhythm	20 Small Squares	75 BPM (1500 / 20)
Regular Rhythm	3 Large Squares	100 BPM (300 / 3)
Irregular Rhythm	9 complexes in 6s	90 BPM (9 × 10)

Normal Heart Rate Ranges

• Normal Sinus Rhythm: 60 to 100 beats per minute (BPM).
• Sinus Bradycardia: Less than 60 BPM. Common in athletes or during sleep, but can indicate heart block.
• Sinus Tachycardia: Greater than 100 BPM. Can be caused by exercise, stress, fever, or underlying cardiac issues.

Medical Disclaimer: This calculator is for educational purposes only. ECG interpretation should always be performed by a qualified healthcare professional who can consider the clinical context of the patient.