How to Calculate Heart Rate from Ecg with Regular Rhythm

ECG Heart Rate Calculator (Regular Rhythm)

1500 Method (Small Squares – More Accurate) 300 Method (Large Squares – Estimation)

Count the squares between two consecutive R-wave peaks.

Estimated Heart Rate:

— BPM

function updateLabel() { var method = document.getElementById("calcMethod").value; var label = document.getElementById("inputLabel"); var input = document.getElementById("rrIntervalCount"); if (method === "300") { label.innerText = "Number of Large Squares between R-R:"; input.placeholder = "e.g. 4"; } else { label.innerText = "Number of Small Squares between R-R:"; input.placeholder = "e.g. 20"; } } function calculateECG() { var method = document.getElementById("calcMethod").value; var count = parseFloat(document.getElementById("rrIntervalCount").value); var resultDiv = document.getElementById("ecgResult"); var bpmOutput = document.getElementById("bpmOutput"); var statusOutput = document.getElementById("rhythmStatus"); if (!count || count <= 0) { alert("Please enter a valid number of squares greater than 0."); return; } var heartRate = 0; var constant = parseInt(method); // Calculation Logic // HR = Constant / Number of Squares heartRate = constant / count; // Round to nearest whole number heartRate = Math.round(heartRate); resultDiv.style.display = "block"; bpmOutput.innerText = heartRate + " BPM"; // Interpretation Logic if (heartRate = 60 && heartRate 100) { statusOutput.innerText = "Interpretation: Tachycardia (Fast Heart Rate)"; statusOutput.style.color = "#c0392b"; } }

How to Calculate Heart Rate from ECG with Regular Rhythm

Electrocardiograms (ECGs or EKGs) are fundamental tools in cardiology for assessing heart rhythm and rate. When the heart rhythm is regular—meaning the distance between consecutive R waves (the R-R interval) is consistent—calculating the heart rate is a straightforward mathematical process based on the speed of the ECG paper.

Understanding ECG Paper Grid

Standard ECG paper moves at a speed of 25 mm/second. The grid printed on the paper helps in measuring time and amplitude:

• Small Square (1mm): Represents 0.04 seconds.
• Large Square (5mm): Represents 0.20 seconds (contains 5 small squares).

Method 1: The 1500 Method (Most Accurate)

The 1500 method is the most precise way to calculate heart rate for regular rhythms. It uses the small squares on the ECG grid.

Formula: Heart Rate = 1500 ÷ Number of Small Squares between R-R

Why 1500? There are 1,500 small squares in one minute of ECG tracing (25mm/sec × 60 sec/min = 1,500 mm/min).

Example: If there are 20 small squares between two R waves, the heart rate is 1500 ÷ 20 = 75 BPM.

Method 2: The 300 Method (Quick Estimation)

The 300 method is faster and useful for quick visual estimation in a clinical setting. It uses the large squares.

Formula: Heart Rate = 300 ÷ Number of Large Squares between R-R

Why 300? There are 300 large squares in one minute (1,500 small squares ÷ 5 = 300).

Sequence: You can memorize the sequence for large squares: 300, 150, 100, 75, 60, 50. If the R-R interval is 1 large square, the rate is 300; if 2 squares, 150; if 4 squares, 75 BPM.

Interpreting the Results

Once you have calculated the heart rate in Beats Per Minute (BPM), you can categorize the rate:

• Normal Sinus Rhythm: 60 – 100 BPM
• Sinus Bradycardia: Less than 60 BPM
• Sinus Tachycardia: Greater than 100 BPM

Note: This calculator is designed for regular rhythms. For irregular rhythms (such as Atrial Fibrillation), the 6-second strip method is generally required.