Uses the Karvonen Formula for increased accuracy by incorporating resting heart rate.
Best measured right after waking up, before getting out of bed.
Please enter valid numbers for age and resting heart rate.
Estimated Maximum Heart Rate (MHR):bpm
Moderate Intensity Zone (50% – 70%): – bpm Best for fat burning and building endurance base.
Vigorous Intensity Zone (70% – 85%): – bpm Best for cardiovascular fitness and increasing capacity.
function calculateHeartRateZones() {
var ageInput = document.getElementById("hrUserAge");
var rhrInput = document.getElementById("hrRestingRate");
var resultsArea = document.getElementById("hr-results-area");
var errorDiv = document.getElementById("hrErrorMessage");
var age = parseInt(ageInput.value);
var rhr = parseInt(rhrInput.value);
// Basic validation
if (isNaN(age) || age 120 || isNaN(rhr) || rhr 150) {
errorDiv.style.display = "block";
resultsArea.style.display = "none";
return;
}
errorDiv.style.display = "none";
// 1. Calculate Maximum Heart Rate (MHR) – Standard formula
var mhr = 220 – age;
// Ensure RHR isn't higher than MHR (rare but possible with bad input)
if (rhr >= mhr) {
errorDiv.innerText = "Resting heart rate cannot be higher than maximum heart rate.";
errorDiv.style.display = "block";
resultsArea.style.display = "none";
return;
}
// 2. Calculate Heart Rate Reserve (HRR) – Karvonen Method
var hrr = mhr – rhr;
// 3. Calculate Moderate Zone (50% – 70%)
// Formula: (HRR * intensity%) + RHR
var modLow = Math.round((hrr * 0.50) + rhr);
var modHigh = Math.round((hrr * 0.70) + rhr);
// 4. Calculate Vigorous Zone (70% – 85%)
// Note: The lower boundary of vigorous usually overlaps the upper boundary of moderate
var vigLow = Math.round((hrr * 0.70) + rhr);
var vigHigh = Math.round((hrr * 0.85) + rhr);
// Display Results
document.getElementById("resultMHR").innerText = mhr;
document.getElementById("resultModLow").innerText = modLow;
document.getElementById("resultModHigh").innerText = modHigh;
document.getElementById("resultVigLow").innerText = vigLow;
document.getElementById("resultVigHigh").innerText = vigHigh;
resultsArea.style.display = "block";
}
Optimizing Your Workout with Target Heart Rate Zones
To maximize the benefits of cardiovascular exercise—whether your goal is weight loss, improved stamina, or peak athletic performance—it is crucial to train at the right intensity. Your heart rate is the most reliable gauge of that intensity. By identifying your specific target heart rate zones, you can ensure every workout is effective and safe.
While many generic charts exist, the most accurate way to determine your personal zones is by factoring in both your age and your current fitness level, measured by your resting heart rate. The calculator above uses the Karvonen Formula, widely regarded by exercise physiologists as a superior method for calculating target intensity because it accounts for your heart rate reserve.
Understanding the Key Metrics
Maximum Heart Rate (MHR): This is the highest number of beats per minute (bpm) your heart can achieve during maximal physical exertion. The standard estimate used here is 220 minus your age.
Resting Heart Rate (RHR): This is the number of times your heart beats per minute while completely at rest. A lower RHR generally indicates better cardiovascular fitness.
Heart Rate Reserve (HRR): This is the difference between your Maximum Heart Rate and your Resting Heart Rate. It represents the cushion you have available for exercise intensity.
Decoding Exercise Intensity Zones
Different training goals require different levels of exertion. Here is what the zones calculated above mean for your training:
Moderate Intensity Zone (50% – 70% of HRR)
Training in this zone feels somewhat hard. You should be breathing heavier than normal but still able to carry on a conversation. This zone is ideal for:
Building a solid base of endurance.
Maximize fat utilization as a fuel source.
Recovery days or longer duration sessions.
Example: A 40-year-old with a resting heart rate of 60 bpm might have a moderate zone between roughly 120 bpm and 144 bpm.
Vigorous Intensity Zone (70% – 85% of HRR)
Training in this zone feels hard to very hard. Breathing is deep and rapid, and you can likely only speak a few words at a time. This zone is crucial for:
Improving cardiovascular capacity (VO2 Max).
Increasing your anaerobic threshold.
Burning a higher total number of calories in a shorter period.
Example: That same 40-year-old might aim for a vigorous zone between roughly 144 bpm and 162 bpm for high-intensity intervals or tempo runs.
How to Use This Information
Use the calculator above to determine your personal ranges. During exercise, monitor your heart rate using a smartwatch, chest strap, or by taking your pulse manually for 10 seconds and multiplying by six. Aim to stay within your target zone for the duration of your workout to ensure you are meeting your specific fitness objectives safely.