ECG Heart Rate Calculator
This calculator estimates heart rate from an Electrocardiogram (ECG) based on the R-R interval. A standard ECG strip records electrical activity at a speed of 25 mm/sec. Each small box on the ECG paper is 1 mm wide, representing 0.04 seconds. Each large box (5 small boxes) is 5 mm wide, representing 0.20 seconds.
OR
Understanding ECG Heart Rate Calculation
An Electrocardiogram (ECG or EKG) is a vital diagnostic tool that records the electrical activity of the heart. One of the most common calculations performed using an ECG is determining the heart rate, which is the number of times the heart beats per minute (BPM).
There are several reliable methods to calculate heart rate from an ECG strip, each suited to different situations and the clarity of the ECG recording. The most common methods rely on the R-R interval, which is the time between two consecutive R waves (the sharp, upward spikes representing ventricular depolarization).
Method 1: Using Small Boxes (Most Accurate for Irregular Rhythms)
This method is considered the most accurate, especially when the heart rhythm is irregular. The standard ECG paper speed is 25 mm/sec, meaning each small box (1 mm) represents 0.04 seconds. To calculate heart rate:
- Count the number of small boxes between two consecutive R waves (the R-R interval).
- Divide 1500 by this number.
Formula: Heart Rate (BPM) = 1500 / (Number of Small Boxes between R-R peaks)
Method 2: Using Large Boxes
Large boxes on ECG paper are typically composed of 5 small boxes, representing 0.20 seconds. This method is quicker but less precise than using small boxes, and is best for regular rhythms.
- Count the number of large boxes between two consecutive R waves.
- Divide 300 by this number.
Formula: Heart Rate (BPM) = 300 / (Number of Large Boxes between R-R peaks)
Method 3: Using R-R Interval in Seconds
If you know the exact duration of the R-R interval in seconds, you can directly calculate the heart rate.
- Measure the R-R interval in seconds.
- Multiply this interval by 60 (to convert seconds to minutes).
- Divide 60 by the R-R interval.
Formula: Heart Rate (BPM) = 60 / (R-R Interval in Seconds)
Our calculator allows you to input either the number of small boxes, large boxes, or the R-R interval in seconds to get an estimate of the heart rate.
function calculateHeartRate() { var rrIntervalSmallBoxes = document.getElementById("rrIntervalSmallBoxes").value; var rrIntervalLargeBoxes = document.getElementById("rrIntervalLargeBoxes").value; var rrIntervalSeconds = document.getElementById("rrIntervalSeconds").value; var resultDiv = document.getElementById("result"); var heartRate = NaN; if (rrIntervalSmallBoxes && !isNaN(parseFloat(rrIntervalSmallBoxes)) && rrIntervalSmallBoxes > 0) { heartRate = 1500 / parseFloat(rrIntervalSmallBoxes); } else if (rrIntervalLargeBoxes && !isNaN(parseFloat(rrIntervalLargeBoxes)) && rrIntervalLargeBoxes > 0) { heartRate = 300 / parseFloat(rrIntervalLargeBoxes); } else if (rrIntervalSeconds && !isNaN(parseFloat(rrIntervalSeconds)) && rrIntervalSeconds > 0) { heartRate = 60 / parseFloat(rrIntervalSeconds); } else { resultDiv.innerHTML = "Please enter valid numerical values for at least one input."; return; } if (!isNaN(heartRate)) { resultDiv.innerHTML = "Estimated Heart Rate: " + heartRate.toFixed(2) + " BPM"; } else { resultDiv.innerHTML = "Could not calculate heart rate. Please check your inputs."; } }