How to Calculate Heart Rate from Cardiac Cycle Graph

Cardiac Cycle Heart Rate Calculator

Calculate BPM from ECG/EKG Graph Data

Calculated Heart Rate:

0 BPM

Normal

function calculateHeartRate() { var intervalSec = document.getElementById("intervalSeconds").value; var smallSq = document.getElementById("smallSquares").value; var largeSq = document.getElementById("largeSquares").value; var resultDiv = document.getElementById("hrResultArea"); var bpmText = document.getElementById("finalBPM"); var categoryText = document.getElementById("hrCategory"); var bpm = 0; if (intervalSec && intervalSec > 0) { bpm = 60 / parseFloat(intervalSec); } else if (smallSq && smallSq > 0) { // On standard ECG paper (25mm/s), small square is 0.04s. 1500 small squares = 60 seconds. bpm = 1500 / parseFloat(smallSq); } else if (largeSq && largeSq > 0) { // One large square = 5 small squares. 300 large squares = 60 seconds. bpm = 300 / parseFloat(largeSq); } else { alert("Please enter at least one measurement value."); return; } bpm = Math.round(bpm); bpmText.innerText = bpm + " BPM"; resultDiv.style.display = "block"; if (bpm 100) { categoryText.innerText = "Tachycardia (Fast)"; categoryText.style.color = "#e64a19"; } else { categoryText.innerText = "Normal Sinus Rhythm"; categoryText.style.color = "#388e3c"; } }

How to Calculate Heart Rate from a Cardiac Cycle Graph

A cardiac cycle graph, commonly known as an Electrocardiogram (ECG or EKG), represents the electrical activity of the heart over time. To calculate the heart rate from this graph, you need to identify the R waves—the highest peaks in the QRS complex.

The Core Formula

The time between two consecutive R peaks is called the R-R interval. The simplest formula to find beats per minute (BPM) is:

Heart Rate (BPM) = 60 / R-R Interval (in seconds)

Common Methods for Manual Calculation

• The 1500 Method: On standard ECG paper moving at 25 mm/sec, one small 1mm square represents 0.04 seconds. Since there are 1,500 small squares in one minute, count the small squares between two R waves and divide 1500 by that number.
• The 300 Method: Each large square (5mm) represents 0.2 seconds. There are 300 large squares in a minute. Count the large squares between R waves and divide 300 by that number.
• The 6-Second Method: If the rhythm is irregular, count the number of R peaks in a 6-second strip (usually 30 large squares) and multiply by 10.

Step-by-Step Calculation Example

Imagine you have an ECG strip with the following data:

1. Locate two consecutive R peaks on the graph.
2. Count the squares between them. Let's say there are 20 small squares.
3. Using the 1500 Method: 1500 / 20 = 75 BPM.
4. Alternatively, if you measure the time directly and find the R-R interval is 0.8 seconds, the calculation is 60 / 0.8 = 75 BPM.

Important Terminology

R-R Interval: The duration between the peak of one QRS complex and the next. This represents one full cardiac cycle.

Paper Speed: Most clinical ECGs are printed at 25 mm per second. If your graph uses a different speed (like 50 mm/s), the constant numbers (1500 and 300) must be doubled.

Sinus Rhythm: A normal heart rate typically falls between 60 and 100 BPM. Results below 60 indicate Bradycardia, while results above 100 indicate Tachycardia.