Please enter a realistic Resting Heart Rate (e.g., between 30 and 200 BPM).
';
return;
}
// 3. Core Calculations (Karvonen Method)
// Estimate Maximum Heart Rate (MHR) using standard formula
var mhr = 220 – age;
if (rhr >= mhr) {
resultArea.innerHTML = '
Error: Your Resting Heart Rate cannot be higher than or equal to your estimated Maximum Heart Rate (' + mhr + ' BPM). Please check your inputs.
';
return;
}
// Calculate Heart Rate Reserve (HRR)
var hrr = mhr – rhr;
// Helper function for Karvonen formula: TargetHR = (HRR * intensity%) + RHR
function getTargetHR(intensityDecimal) {
return Math.round((hrr * intensityDecimal) + rhr);
}
// Calculate Zone Boundaries
var z1_end = getTargetHR(0.60);
var z2_end = getTargetHR(0.70);
var z3_end = getTargetHR(0.80);
var z4_end = getTargetHR(0.90);
// Zone 5 ends at MHR
var z5_end = mhr;
// 4. Generate Output HTML
var outputHtml = ";
outputHtml += '
';
outputHtml += 'Based on age ' + age + ' and a resting heart rate of ' + rhr + ' BPM:';
outputHtml += 'Your estimated Maximum Heart Rate is: ' + mhr + ' BPM.';
outputHtml += '
';
// Zone 2: 60-70% (start at previous end + 1)
outputHtml += '
Zone 2
Light / Fat Burn
' + (z1_end + 1) + ' – ' + z2_end + ' BPM
';
// Zone 3: 70-80%
outputHtml += '
Zone 3
Moderate / Aerobic
' + (z2_end + 1) + ' – ' + z3_end + ' BPM
';
// Zone 4: 80-90%
outputHtml += '
Zone 4
Hard / Anaerobic Threshold
' + (z3_end + 1) + ' – ' + z4_end + ' BPM
';
// Zone 5: 90-100%
outputHtml += '
Zone 5
Maximum Effort / VO2 Max
' + (z4_end + 1) + ' – ' + z5_end + ' BPM
';
outputHtml += '
';
// 5. Display Result
resultArea.innerHTML = outputHtml;
}
Understanding Your Heart Rate Zones for Smarter Training
Training based on heart rate is one of the most effective ways to achieve specific fitness goals, whether you are looking to burn fat, improve cardiovascular endurance, or increase peak athletic performance. Rather than guessing your effort level, heart rate training uses objective data—measured in beats per minute (BPM)—to ensure you are training at the right intensity.
This calculator uses the Karvonen Method to define your training zones. Unlike simpler calculators that only look at a percentage of your maximum heart rate, the Karvonen formula incorporates your Resting Heart Rate (RHR). This accounts for your current fitness level, providing more personalized and accurate training bands than standard age-based formulas alone.
What Do the Zones Mean?
The calculator above divides your training intensity into five distinct zones:
Zone 1 (Very Light, 50-60%): Used for warm-ups, cool-downs, and active recovery. It aids blood flow and helps muscles recover without placing stress on the body.
Zone 2 (Light, 60-70%): Often called the "fat-burning zone." Training here improves basic endurance and teaches your body to utilize fat as its primary fuel source efficiently. You should be able to hold a conversation easily.
Zone 3 (Moderate, 70-80%): The "aerobic zone." This improves your cardiovascular system's ability to transport oxygen. It builds foundational fitness and stamina for longer durations.
Zone 4 (Hard, 80-90%): This is where you push your anaerobic threshold. Training here improves your body's ability to deal with lactic acid, allowing you to sustain higher intensities for longer.
Zone 5 (Maximum, 90-100%): Peak effort used for very short intervals. This zone improves top-end speed and neuromuscular power. It is highly demanding and should be used sparingly.
How to Use These Results
To use these zones effectively, you need a device to measure your heart rate during exercise, such as a chest strap monitor or a smart watch. Once you know your zones, you can structure your workouts accordingly. For example, a long weekend run might be targeted purely in Zone 2, while a mid-week interval session might alternate between Zone 4 efforts and Zone 1 recoveries.
Important Note: The maximum heart rate calculation used here (220 minus Age) is a standard estimation. Your actual maximum heart rate may vary. For the most accurate zones, consider having a professional VO2 max or metabolic test performed. Always consult with a physician before starting any new exercise program, especially if you have existing health conditions.