Count the 1mm small squares between two consecutive R-waves.
Calculated Heart Rate
0 BPM
function calculateECG() {
var boxesInput = document.getElementById('smallBoxes');
var resultBox = document.getElementById('resultOutput');
var bpmDisplay = document.getElementById('bpmValue');
var statusDisplay = document.getElementById('rhythmStatus');
var smallBoxes = parseFloat(boxesInput.value);
// Validation
if (!smallBoxes || smallBoxes <= 0) {
alert("Please enter a valid number of small boxes greater than 0.");
return;
}
// The 1500 Method Formula: 1500 / Number of Small Boxes
var bpm = 1500 / smallBoxes;
// Round to nearest integer
var roundedBpm = Math.round(bpm);
// Determine Rhythm Status
var statusText = "";
var statusClass = "";
if (roundedBpm = 60 && roundedBpm <= 100) {
statusText = "Normal Sinus Rhythm";
statusClass = "status-normal";
} else {
statusText = "Sinus Tachycardia (Fast Heart Rate)";
statusClass = "status-tachy";
}
// Display Logic
bpmDisplay.innerHTML = roundedBpm + " BPM";
statusDisplay.innerHTML = statusText;
statusDisplay.className = "ecg-interpretation " + statusClass;
resultBox.style.display = "block";
}
Understanding the 1500 Method for ECG Calculation
The 1500 Method is considered the most precise technique for calculating heart rate from an Electrocardiogram (ECG) strip, specifically when the heart rhythm is regular. Unlike the "300 Method" (which counts large boxes) or the "6-Second Method" (used for irregular rhythms), the 1500 method utilizes the smallest unit of measurement on the ECG paper for higher accuracy.
Formula: Heart Rate = 1500 ÷ Number of Small Boxes between R-R Interval
How the Math Works
Standard ECG paper moves at a speed of 25 millimeters per second (mm/s).
There are 60 seconds in one minute.
Total distance covered in one minute = 25 mm/s × 60 s = 1500 mm/min.
Since each small box on the paper represents 1 mm, there are 1500 small boxes passing through the machine every minute.
By dividing 1500 by the number of small boxes between two heartbeats (the R-R interval), you calculate exactly how many times that interval would fit into one minute.
Step-by-Step Calculation Guide
Locate the R-Waves: Identify two consecutive QRS complexes. The "R" wave is typically the tallest upward spike.
Count the Small Boxes: carefully count the number of 1mm squares between the peak of the first R-wave and the peak of the next R-wave.
Apply the Division: Take the number 1500 and divide it by your count.
Example Scenario
If you count 20 small boxes between two consecutive R-waves:
Calculation: 1500 ÷ 20 = 75
The heart rate is 75 BPM, which indicates a normal sinus rhythm.
Interpreting Your Results
For a standard resting adult, heart rates are classified as follows:
Bradycardia: Less than 60 BPM. This may be normal for athletes or during sleep, but can indicate pathology in others.
Normal Sinus Rhythm: 60 to 100 BPM.
Tachycardia: Greater than 100 BPM. This can be caused by exercise, stress, fever, or cardiac arrhythmias.
Note: This calculator assumes standard paper speed of 25 mm/s. If the ECG was recorded at 50 mm/s, the constant would change from 1500 to 3000.