Calculating Heart Rate Using Rr Interval

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RR Interval to Heart Rate Calculator

Milliseconds (ms) Seconds (s)

Understanding the RR Interval and Heart Rate

The RR interval is the time elapsed between two successive R waves on an electrocardiogram (ECG/EKG). This measurement is fundamental in cardiology for determining the instantaneous heart rate and assessing heart rate variability (HRV).

The Calculation Formula

Because there are 60 seconds in a minute, the relationship between the RR interval and Heart Rate (BPM) is inverse. The formulas used in this calculator are:

  • If measured in Milliseconds: Heart Rate (BPM) = 60,000 / RR Interval (ms)
  • If measured in Seconds: Heart Rate (BPM) = 60 / RR Interval (s)

Clinical Interpretation

For a healthy adult at rest, a normal heart rate typically ranges from 60 to 100 BPM. Here is how results are generally classified:

BPM Range Classification
Below 60 BPM Bradycardia (Slow)
60 – 100 BPM Normal Resting Heart Rate
Above 100 BPM Tachycardia (Fast)

Example Calculation

If an ECG strip shows an RR interval of 800ms:

60,000 / 800 = 75 Beats Per Minute (BPM).

This falls within the normal range for a resting adult.

function calculateHR() { var rrValue = parseFloat(document.getElementById('rrValue').value); var rrUnit = document.getElementById('rrUnit').value; var resultArea = document.getElementById('hrResultArea'); var valueDisplay = document.getElementById('hrValueDisplay'); var statusDisplay = document.getElementById('hrStatusDisplay'); if (isNaN(rrValue) || rrValue <= 0) { alert("Please enter a valid positive number for the RR interval."); return; } var heartRate; if (rrUnit === 'ms') { heartRate = 60000 / rrValue; } else { heartRate = 60 / rrValue; } var roundedHR = Math.round(heartRate * 100) / 100; resultArea.style.display = 'block'; valueDisplay.innerHTML = roundedHR + " BPM"; var status = ""; var color = ""; var bgColor = ""; if (roundedHR = 60 && roundedHR <= 100) { status = "Classification: Normal Range"; color = "#155724"; bgColor = "#d4edda"; } else { status = "Classification: Tachycardia (Fast)"; color = "#856404"; bgColor = "#fff3cd"; } resultArea.style.backgroundColor = bgColor; statusDisplay.style.color = color; statusDisplay.innerHTML = status; }

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