Calculating Heart Rate Ecg Rhythm Strip

ECG Heart Rate Calculator

Calculate BPM using standard ECG rhythm strip methods

1500 Method (Precise – Small Boxes) 300 Method (Quick – Large Boxes) 6-Second Strip (Irregular Rhythms)

function updateInputs() { var method = document.getElementById('calcMethod').value; var label = document.getElementById('inputLabel'); var input = document.getElementById('inputValue'); if (method === '1500') { label.innerText = 'Number of Small Boxes (between two R waves):'; input.placeholder = 'e.g. 20'; } else if (method === '300') { label.innerText = 'Number of Large Boxes (between two R waves):'; input.placeholder = 'e.g. 4'; } else { label.innerText = 'Number of QRS Complexes (in a 6-second strip):'; input.placeholder = 'e.g. 7'; } document.getElementById('ecgResult').style.display = 'none'; } function calculateECG() { var method = document.getElementById('calcMethod').value; var val = parseFloat(document.getElementById('inputValue').value); var resultDiv = document.getElementById('ecgResult'); var resVal = document.getElementById('resultValue'); var resCat = document.getElementById('resultCategory'); var bpm = 0; if (isNaN(val) || val <= 0) { alert('Please enter a valid positive number'); return; } if (method === '1500') { bpm = 1500 / val; } else if (method === '300') { bpm = 300 / val; } else if (method === '6sec') { bpm = val * 10; } bpm = Math.round(bpm); resVal.innerText = bpm + ' BPM'; resultDiv.style.display = 'block'; if (bpm 100) { resCat.innerText = 'Tachycardia'; resCat.style.color = '#d32f2f'; resultDiv.style.backgroundColor = '#ffebee'; } else { resCat.innerText = 'Normal Sinus Rhythm'; resCat.style.color = '#388e3c'; resultDiv.style.backgroundColor = '#e8f5e9'; } }

Calculating the heart rate from an Electrocardiogram (ECG/EKG) strip is a fundamental skill in clinical medicine. Standard ECG paper moves at a constant speed of 25 mm/second, which allows us to use distance (boxes) to measure time and frequency.

The 1500 Method (The Most Precise)

The 1500 method is used for regular rhythms. Because there are 1,500 small boxes in one minute of ECG paper (60 seconds / 0.04 seconds per small box), you can find the exact rate by dividing 1500 by the number of small boxes between two consecutive R waves (the R-R interval).

Example: If there are 15 small boxes between two R waves, the heart rate is 1500 ÷ 15 = 100 BPM.

The 300 Method (The Sequence Method)

This is a quick mental math version of the 1500 method, also for regular rhythms. There are 300 large boxes in one minute. Divide 300 by the number of large boxes between R waves.

Example: If there are 4 large boxes between R waves, the heart rate is 300 ÷ 4 = 75 BPM.

The 6-Second Method (For Irregular Rhythms)

When the rhythm is irregular (like Atrial Fibrillation), the box methods are inaccurate. Instead, count the number of QRS complexes on a 6-second strip and multiply by 10. Most ECG strips have markings at the top indicating 3-second or 1-second intervals.

Example: If you count 8 QRS complexes in a 6-second window, the estimated heart rate is 8 × 10 = 80 BPM.

Quick Reference Table

Large Boxes	BPM (Approx)	Classification
1 Box	300	Extreme Tachycardia
3 Boxes	100	Upper Normal Limit
5 Boxes	60	Lower Normal Limit
6+ Boxes	< 50	Bradycardia

Note: This tool is for educational purposes only. Always consult a qualified healthcare professional for medical diagnosis and treatment.