Understanding your heart rate range is essential for effective cardiovascular training. Instead of a generic formula, the Karvonen Formula is considered the gold standard because it accounts for your unique resting heart rate.
The Math Behind the Calculation
The calculation follows four distinct steps:
Max Heart Rate (MHR): Calculate your ceiling by subtracting your age from 220. (220 – Age = MHR).
Heart Rate Reserve (HRR): Subtract your resting heart rate from your maximum. (MHR – RHR = HRR).
Target Zone Calculation: Multiply HRR by the desired intensity percentage (e.g., 50% or 0.50).
Final Range: Add your resting heart rate back to that number. ( (HRR × Intensity) + RHR = Target HR ).
Example Calculation
Imagine a 40-year-old individual with a resting heart rate of 70 BPM who wants to train at 60% intensity:
1. MHR: 220 – 40 = 180 BPM
2. HRR: 180 – 70 = 110 BPM
3. Intensity: 110 × 0.60 = 66
4. Result: 66 + 70 = 136 BPM
Heart Rate Zones Explained
Moderate Intensity (50-70%): Ideal for beginners, warm-ups, and building basic endurance. You can still hold a conversation comfortably.
Vigorous Intensity (70-85%): Improves aerobic capacity and cardiovascular fitness. Talking becomes difficult at this level.
Peak Intensity (85%+): Used for high-intensity interval training (HIIT) and competitive performance. This level can only be sustained for short durations.
Note: Always consult with a physician before starting a new vigorous exercise program, especially if you have existing heart conditions or are taking medication that affects heart rate.
function calculateHeartRateRange() {
var age = document.getElementById('calcAge').value;
var restingHR = document.getElementById('calcRestingHR').value;
var resultArea = document.getElementById('hrResultsArea');
if (age === "" || restingHR === "" || age <= 0 || restingHR <= 0) {
alert("Please enter a valid age and resting heart rate.");
return;
}
var ageNum = parseFloat(age);
var rhrNum = parseFloat(restingHR);
// Basic Max HR Calculation
var mhr = 220 – ageNum;
// Heart Rate Reserve
var hrr = mhr – rhrNum;
if (hrr <= 0) {
alert("Resting heart rate cannot be higher than maximum heart rate. Please check your inputs.");
return;
}
// Zone Calculations
var modLow = Math.round((hrr * 0.50) + rhrNum);
var modHigh = Math.round((hrr * 0.70) + rhrNum);
var vigLow = Math.round((hrr * 0.70) + rhrNum);
var vigHigh = Math.round((hrr * 0.85) + rhrNum);
var peakLow = Math.round((hrr * 0.85) + rhrNum);
var peakHigh = mhr;
// Output results
document.getElementById('resMHR').innerText = mhr;
document.getElementById('resHRR').innerText = hrr;
document.getElementById('rangeModerate').innerText = modLow + " – " + modHigh + " BPM";
document.getElementById('rangeVigorous').innerText = vigLow + " – " + vigHigh + " BPM";
document.getElementById('rangePeak').innerText = peakLow + " – " + peakHigh + " BPM";
resultArea.style.display = 'block';
// Smooth scroll to results
resultArea.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}