Please enter a valid positive number for the RR interval.
Calculated Heart Rate
0 BPM
function calculateBPM() {
var rrInput = document.getElementById('rr_interval');
var unitSelect = document.getElementById('rr_unit');
var resultContainer = document.getElementById('result_container');
var bpmDisplay = document.getElementById('bpm_result');
var classDisplay = document.getElementById('hr_classification');
var errorMsg = document.getElementById('error_msg');
var rrValue = parseFloat(rrInput.value);
var unit = unitSelect.value;
// Reset display
errorMsg.style.display = 'none';
resultContainer.style.display = 'none';
classDisplay.className = 'result-classification'; // remove color classes
// Validation
if (isNaN(rrValue) || rrValue <= 0) {
errorMsg.style.display = 'block';
return;
}
// Calculation Logic
var bpm = 0;
// Formula: BPM = 60,000 / RR(ms) OR 60 / RR(s)
if (unit === 'ms') {
bpm = 60000 / rrValue;
} else {
bpm = 60 / rrValue;
}
// Display Result
resultContainer.style.display = 'block';
bpmDisplay.innerHTML = bpm.toFixed(1) + " BPM";
// Classification Logic
var classificationText = "";
var classificationClass = "";
if (bpm = 60 && bpm <= 100) {
classificationText = "Normal Sinus Rhythm";
classificationClass = "class-normal";
} else {
classificationText = "Tachycardia (Fast Heart Rate)";
classificationClass = "class-tachy";
}
classDisplay.innerText = classificationText;
classDisplay.classList.add(classificationClass);
}
Understanding the RR Interval to Heart Rate Calculation
The RR interval is a critical metric derived from an Electrocardiogram (ECG or EKG). It represents the time elapsed between two successive R-waves of the QRS signal. This interval is essentially the duration of one complete cardiac cycle, usually measured in milliseconds (ms) or seconds (s).
Calculating the heart rate (in Beats Per Minute, or BPM) from the RR interval is a fundamental process in cardiology and physiological monitoring. It allows for the instantaneous determination of heart rate, which is vital for analyzing Heart Rate Variability (HRV) and detecting arrhythmias.
The Formula
The mathematical relationship between the RR interval and heart rate is inversely proportional. The formula depends on the unit of measurement used for the RR interval:
If RR Interval is in Milliseconds (ms):
Heart Rate (BPM) = 60,000 ÷ RR Interval
If RR Interval is in Seconds (s):
Heart Rate (BPM) = 60 ÷ RR Interval
Calculation Examples
Here are a few practical examples of how the conversion works:
RR Interval (ms)
RR Interval (s)
Heart Rate (BPM)
Classification
1500 ms
1.5 s
40 BPM
Bradycardia
1000 ms
1.0 s
60 BPM
Normal Low
800 ms
0.8 s
75 BPM
Normal Average
600 ms
0.6 s
100 BPM
Normal High
400 ms
0.4 s
150 BPM
Tachycardia
Clinical Interpretations
Once you have converted the RR interval to BPM, the result is typically categorized into three main clinical zones:
Bradycardia (< 60 BPM): A slower than normal heart rate. This is often common in endurance athletes during rest but can indicate heart block or other cardiac issues in sedentary individuals.
Normal Sinus Rhythm (60 – 100 BPM): The standard resting heart rate range for healthy adults.
Tachycardia (> 100 BPM): A faster than normal heart rate. While normal during exercise or stress, a resting rate above 100 BPM may require medical investigation.
Why Measure RR Intervals?
While average heart rate provides a snapshot of cardiovascular effort, the specific measurement of RR intervals allows for the analysis of Heart Rate Variability (HRV). HRV is the fluctuation in the time intervals between adjacent heartbeats.
A consistent RR interval (low HRV) implies a "metronomic" heart beat, often associated with stress or sympathetic nervous system dominance. Highly variable RR intervals (high HRV) generally indicate good cardiovascular fitness and a responsive parasympathetic nervous system (rest and digest).
Frequently Asked Questions
Is a lower RR interval better?
No. A lower RR interval means the time between beats is shorter, which results in a higher heart rate. Conversely, a higher RR interval indicates a slower heart rate.
How accurate is this calculation?
The math is exact. However, the accuracy depends on the precision of the device measuring the R-waves (e.g., a Holter monitor, chest strap, or medical ECG). Optical heart rate sensors (PPG) measure pulse intervals, which are slightly different but often used as a proxy.