How to Calculate Heart Rate in Ecg Paper

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ECG Heart Rate Calculator

Big Box Method (300 / Big Boxes) Small Box Method (1500 / Small Boxes) 6-Second Strip Method (R-waves × 10)
function toggleInputs() { var method = document.getElementById("ecgMethod").value; var label = document.getElementById("inputLabel"); var input = document.getElementById("ecgInputValue"); if (method === "bigBox") { label.innerText = "Number of Large Squares (R-R interval):"; input.placeholder = "e.g., 4"; } else if (method === "smallBox") { label.innerText = "Number of Small Squares (R-R interval):"; input.placeholder = "e.g., 20"; } else { label.innerText = "Number of R-waves (in a 6-second strip):"; input.placeholder = "e.g., 8"; } document.getElementById("ecgResult").style.display = "none"; } function calculateHeartRate() { var method = document.getElementById("ecgMethod").value; var value = parseFloat(document.getElementById("ecgInputValue").value); var resultDiv = document.getElementById("ecgResult"); var output = document.getElementById("heartRateOutput"); var interpretation = document.getElementById("interpretationText"); var heartRate = 0; if (isNaN(value) || value <= 0) { alert("Please enter a valid positive number."); return; } if (method === "bigBox") { heartRate = 300 / value; } else if (method === "smallBox") { heartRate = 1500 / value; } else { heartRate = value * 10; } var finalHR = Math.round(heartRate); output.innerText = finalHR + " BPM"; var interpret = ""; if (finalHR 100) { interpret = "Result: Tachycardia (Fast Heart Rate)"; interpretation.style.color = "#d32f2f"; } else { interpret = "Result: Normal Heart Rate"; interpretation.style.color = "#388e3c"; } interpretation.innerText = interpret; resultDiv.style.display = "block"; }

How to Calculate Heart Rate on ECG Paper

Electrocardiogram (ECG) interpretation is a critical skill for medical professionals. Determining the heart rate accurately from a paper strip is the first step in identifying rhythm abnormalities. ECG paper is standard: it moves at a speed of 25 mm/second, meaning each small square represents 0.04 seconds and each large square represents 0.20 seconds.

Common Methods for ECG Heart Rate Calculation

Depending on whether the heart rhythm is regular or irregular, different mathematical methods are used to determine the Beats Per Minute (BPM).

1. The Big Box Method (300 Method)

This is the fastest method for regular rhythms. You count the number of large squares (5mm) between two consecutive R-waves (the peaks of the QRS complex).

  • Formula: 300 / Number of Large Squares = BPM
  • Example: If there are 3 large squares between R-waves, the heart rate is 300 / 3 = 100 BPM.

2. The Small Box Method (1500 Method)

The small box method is the most accurate for regular rhythms. Since there are 1,500 small squares in one minute of ECG paper, you divide 1,500 by the number of small squares between R-waves.

  • Formula: 1500 / Number of Small Squares = BPM
  • Example: If there are 20 small squares between R-waves, the heart rate is 1500 / 20 = 75 BPM.

3. The 6-Second Strip Method

This is the preferred method for irregular rhythms (like Atrial Fibrillation). Because the R-R interval varies, you cannot rely on a single gap. Instead, you look at a 6-second window of time.

  • Formula: Number of R-waves in 6 seconds × 10 = BPM
  • Note: On standard ECG paper, 30 large boxes equals exactly 6 seconds. Count the peaks within 30 large boxes and multiply by 10.

Interpreting the Results

Once you have calculated the heart rate using our tool or manually, the result is typically classified into three categories for adults:

Heart Rate Classification
Below 60 BPM Bradycardia
60 – 100 BPM Normal Sinus Rhythm
Above 100 BPM Tachycardia

Quick Reference Table

If you are using the Big Box method, here are the standard conversions for quick identification:

  • 1 Big Box = 300 BPM
  • 2 Big Boxes = 1500 BPM
  • 3 Big Boxes = 100 BPM
  • 4 Big Boxes = 75 BPM
  • 5 Big Boxes = 60 BPM
  • 6 Big Boxes = 50 BPM

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