.calc-input-group { margin-bottom: 20px; }
.calc-label { display: block; font-weight: bold; margin-bottom: 8px; font-size: 16px; color: #2c3e50; }
.calc-input { width: 100%; padding: 12px; border: 2px solid #e0e0e0; border-radius: 6px; font-size: 16px; box-sizing: border-box; transition: border-color 0.3s; }
.calc-input:focus { border-color: #e74c3c; outline: none; }
.calc-btn { background-color: #e74c3c; color: white; border: none; padding: 15px 25px; font-size: 18px; font-weight: bold; border-radius: 6px; cursor: pointer; width: 100%; transition: background-color 0.3s; }
.calc-btn:hover { background-color: #c0392b; }
.calc-result { margin-top: 25px; padding: 20px; background-color: #f9f9f9; border-left: 5px solid #e74c3c; border-radius: 4px; }
.result-value { font-size: 24px; font-weight: bold; color: #e74c3c; }
.calc-method-toggle { display: flex; gap: 10px; margin-bottom: 20px; }
.method-btn { flex: 1; padding: 10px; background: #eee; border: 1px solid #ccc; cursor: pointer; border-radius: 4px; font-weight: 500; }
.method-btn.active { background: #e74c3c; color: white; border-color: #e74c3c; }
.hidden { display: none; }
function calculateHeartRate() {
var smallSquares = document.getElementById("smallSquares").value;
var largeSquares = document.getElementById("largeSquares").value;
var isSmallMethod = !document.getElementById("smallSquareGroup").classList.contains("hidden");
var bpm = 0;
if (isSmallMethod) {
var smallVal = parseFloat(smallSquares);
if (isNaN(smallVal) || smallVal <= 0) {
alert("Please enter a valid number of small squares.");
return;
}
bpm = 1500 / smallVal;
} else {
var largeVal = parseFloat(largeSquares);
if (isNaN(largeVal) || largeVal <= 0) {
alert("Please enter a valid number of large squares.");
return;
}
bpm = 300 / largeVal;
}
var finalBpm = Math.round(bpm);
document.getElementById("bpmOutput").innerHTML = finalBpm + " BPM";
var status = "";
var statusColor = "";
if (finalBpm 100) {
status = "Tachycardia (Fast Heart Rate)";
statusColor = "#e74c3c";
} else {
status = "Normal Sinus Rhythm Range";
statusColor = "#27ae60";
}
document.getElementById("rhythmStatus").innerHTML = status;
document.getElementById("rhythmStatus").style.color = statusColor;
document.getElementById("resultArea").classList.remove("hidden");
}
How to Calculate Heart Rate from an ECG Graph
When looking at an Electrocardiogram (ECG/EKG) strip, the paper grid provides a precise way to measure the time interval between heartbeats. The horizontal axis represents time, and by measuring the distance between two consecutive R-waves (the tall spikes), you can determine the Heart Rate (BPM).
The Grid Fundamentals
Standard ECG paper moves at a speed of 25 millimeters per second (mm/s). This standard leads to two common units of measurement on the grid:
- Small Squares: Each small box is 1mm wide, representing 0.04 seconds.
- Large Squares: Each large box (consisting of 5×5 small boxes) is 5mm wide, representing 0.20 seconds.
Calculation Methods
1. The 1500 Method (Most Accurate)
Since there are 1,500 small squares in one minute (60 seconds / 0.04 seconds), you can calculate the heart rate by counting the number of small squares between two R-waves. This is best for regular heart rhythms.
Formula: 1500 / Number of Small Squares = BPM
Example: If there are 20 small squares between R-waves, 1500 / 20 = 75 BPM.
2. The 300 Method (Quick Estimation)
Since there are 300 large squares in one minute (60 seconds / 0.20 seconds), you can count the number of large squares between R-waves for a faster calculation.
Formula: 300 / Number of Large Squares = BPM
Example: If there are 4 large squares between R-waves, 300 / 4 = 75 BPM.
When to Use the 6-Second Method
If the heart rhythm is irregular, the methods above may not be accurate. In these cases, medical professionals use the 6-second strip method. You count the number of R-waves in a 6-second interval (usually marked by small ticks at the top of the paper) and multiply that number by 10.
Formula: Number of Cycles in 6 Seconds x 10 = BPM
Standard Heart Rate Ranges
| Category |
BPM Range |
| Bradycardia |
Less than 60 BPM |
| Normal Range |
60 – 100 BPM |
| Tachycardia |
Greater than 100 BPM |
Disclaimer: This tool is for educational purposes only. If you are experiencing heart palpitations, chest pain, or dizziness, please seek immediate medical attention from a healthcare professional.