Calculating Heart Rate from R-r Interval

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R-R Interval to Heart Rate Calculator

Milliseconds (ms) Seconds (s)
function calculateHR() { var rrValue = parseFloat(document.getElementById('rrInterval').value); var unit = document.getElementById('unit').value; var resultWrapper = document.getElementById('resultWrapper'); var hrResult = document.getElementById('hrResult'); var hrCategory = document.getElementById('hrCategory'); if (isNaN(rrValue) || rrValue <= 0) { alert("Please enter a valid positive number for the R-R interval."); return; } var bpm; if (unit === 'ms') { // Formula: 60,000 / RR in ms bpm = 60000 / rrValue; } else { // Formula: 60 / RR in seconds bpm = 60 / rrValue; } var roundedBPM = Math.round(bpm * 100) / 100; resultWrapper.style.display = 'block'; hrResult.innerHTML = roundedBPM + " BPM"; var category = ""; if (roundedBPM = 60 && roundedBPM <= 100) { category = "Category: Normal Resting Heart Rate"; } else { category = "Category: Tachycardia (High)"; } hrCategory.innerHTML = category; }

Understanding the R-R Interval

In electrocardiography (ECG), the R-R interval represents the time elapsed between two successive R waves (the highest peaks of the QRS complex). This measurement is the most common way to calculate the instantaneous heart rate and is the foundational metric used for Heart Rate Variability (HRV) analysis.

How to Calculate Heart Rate from R-R Intervals

The relationship between the R-R interval and heart rate (BPM) is inversely proportional. The shorter the interval between heartbeats, the faster the heart is beating. The mathematical formulas are as follows:

  • If measuring in Milliseconds (ms): Heart Rate = 60,000 / R-R Interval
  • If measuring in Seconds (s): Heart Rate = 60 / R-R Interval

Practical Examples

To better understand these calculations, consider the following clinical examples:

R-R Interval (ms) R-R Interval (s) Heart Rate (BPM)
600 ms 0.60 s 100 BPM
857 ms 0.857 s 70 BPM
1000 ms 1.00 s 60 BPM

Why R-R Interval Matters

While average heart rate provides a general overview of cardiovascular health, the R-R interval offers specific data for:

  • Arrhythmia Detection: Inconsistent R-R intervals may indicate atrial fibrillation or other irregular heart rhythms.
  • Autonomic Nervous System Balance: Variations in R-R intervals (HRV) indicate how well the body is managing stress and recovery.
  • Athlete Recovery: Coaches use R-R interval data to determine if an athlete is overtraining or ready for high-intensity work.

Disclaimer: This calculator is for educational purposes only. Always consult a medical professional for the interpretation of ECG data or if you suspect cardiac issues.

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