.rr-calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 600px;
margin: 20px auto;
padding: 30px;
background: #ffffff;
border-radius: 12px;
box-shadow: 0 4px 20px rgba(0,0,0,0.08);
border: 1px solid #e0e0e0;
}
.rr-calculator-container h2 {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
}
.rr-input-group {
margin-bottom: 20px;
}
.rr-input-group label {
display: block;
font-weight: 600;
margin-bottom: 8px;
color: #34495e;
}
.rr-input-group input {
width: 100%;
padding: 12px;
font-size: 16px;
border: 1px solid #cbd5e0;
border-radius: 6px;
box-sizing: border-box;
transition: border-color 0.2s;
}
.rr-input-group input:focus {
border-color: #3498db;
outline: none;
}
.rr-btn {
width: 100%;
padding: 14px;
background-color: #e74c3c;
color: white;
border: none;
border-radius: 6px;
font-size: 18px;
font-weight: 600;
cursor: pointer;
transition: background-color 0.2s;
}
.rr-btn:hover {
background-color: #c0392b;
}
.rr-results {
margin-top: 25px;
padding: 20px;
background-color: #f8f9fa;
border-radius: 8px;
border-left: 5px solid #e74c3c;
display: none;
}
.rr-result-item {
margin-bottom: 12px;
display: flex;
justify-content: space-between;
align-items: center;
border-bottom: 1px solid #e9ecef;
padding-bottom: 8px;
}
.rr-result-item:last-child {
border-bottom: none;
margin-bottom: 0;
padding-bottom: 0;
}
.rr-label {
color: #7f8c8d;
font-weight: 500;
}
.rr-value {
font-weight: 700;
color: #2c3e50;
font-size: 1.1em;
}
.error-msg {
color: #e74c3c;
font-size: 14px;
margin-top: 5px;
display: none;
}
.article-section {
max-width: 800px;
margin: 40px auto;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
}
.article-section h2 {
color: #2c3e50;
margin-top: 30px;
border-bottom: 2px solid #ecf0f1;
padding-bottom: 10px;
}
.article-section h3 {
color: #34495e;
margin-top: 25px;
}
.article-section ul {
margin-bottom: 20px;
}
.article-section li {
margin-bottom: 10px;
}
.info-box {
background-color: #e8f4fd;
border-left: 4px solid #3498db;
padding: 15px;
margin: 20px 0;
}
function calculateRR() {
var bpmInput = document.getElementById('bpmInput');
var bpmValue = parseFloat(bpmInput.value);
var errorDiv = document.getElementById('bpmError');
var resultDiv = document.getElementById('rrResults');
// Reset display
errorDiv.style.display = 'none';
resultDiv.style.display = 'none';
// Validation
if (isNaN(bpmValue) || bpmValue <= 0) {
errorDiv.style.display = 'block';
return;
}
// Calculation Logic
// Formula: RR (seconds) = 60 / BPM
// Formula: RR (ms) = (60 / BPM) * 1000
var rrSeconds = 60 / bpmValue;
var rrMilliseconds = rrSeconds * 1000;
var frequencyHz = bpmValue / 60; // Frequency is beats per second (Hz)
// Formatting results
var displayMs = rrMilliseconds.toFixed(2);
var displaySec = rrSeconds.toFixed(4);
var displayHz = frequencyHz.toFixed(3);
// Update DOM
document.getElementById('resMs').innerHTML = displayMs + " ms";
document.getElementById('resSec').innerHTML = displaySec + " s";
document.getElementById('resHz').innerHTML = displayHz + " Hz";
// Show results
resultDiv.style.display = 'block';
}
Understanding the R-R Interval Calculation
The R-R interval is a fundamental metric in cardiology and physiology, representing the time elapsed between two successive R-waves of the QRS complex on an electrocardiogram (ECG). While the Heart Rate (HR) provides an average number of beats per minute, the R-R interval provides the specific duration of a single cardiac cycle.
This calculator converts a standard Heart Rate in Beats Per Minute (BPM) into the R-R interval duration, displayed in both milliseconds (ms) and seconds (s). This conversion is essential for medical professionals, researchers analyzing Heart Rate Variability (HRV), and athletes monitoring physiological recovery.
The Formulas
The relationship between Heart Rate (BPM) and the R-R interval is reciprocal. To convert between the two, we use standard time conversion constants.
Formula for Milliseconds (ms):
R-R Interval (ms) = (60 / Heart Rate) × 1000
Formula for Seconds (s):
R-R Interval (s) = 60 / Heart Rate
Calculation Examples
Here are a few common examples of how heart rate translates to R-R interval duration:
- 60 BPM: 60 / 60 = 1 second (1000 ms). This represents a resting heart rate where each beat occurs exactly one second apart.
- 100 BPM: 60 / 100 = 0.6 seconds (600 ms). A faster heart rate results in a shorter duration between beats.
- 150 BPM: 60 / 150 = 0.4 seconds (400 ms). During intense exercise, the R-R interval shortens significantly.
Why is R-R Interval Important?
While the standard heart rate gives a general overview of cardiac activity, the R-R interval is the raw data used to calculate Heart Rate Variability (HRV). HRV measures the fluctuation in time intervals between adjacent heartbeats.
A constant R-R interval (low HRV) implies the autonomic nervous system is under stress or dominantly sympathetic (fight or flight). Conversely, a fluctuating R-R interval (high HRV) generally indicates a healthy, responsive autonomic nervous system and good recovery status (parasympathetic dominance).
ECG and the QRS Complex
On an ECG strip, the "R" represents the peak of the QRS complex, which corresponds to the depolarization of the ventricles (the main pumping action of the heart). Measuring from the peak of one R-wave to the peak of the next provides the most accurate measure of the cardiac cycle duration, hence the name "R-R Interval".
In clinical settings, tachograms (plots of R-R intervals over time) are used to visualize heart rhythm stability and detect arrhythmias like atrial fibrillation, where the R-R intervals become highly irregular.