Calculate your target heart rate zone for fat burning during exercise.
Understanding Your Fat Burn Heart Rate Zone
The "fat burn" zone is a range of your maximum heart rate where your body is thought to efficiently burn a higher percentage of calories from fat. This doesn't necessarily mean you burn *more* total calories, but the proportion of fat used as fuel is higher within this zone.
How it's Calculated:
The most common method to estimate your maximum heart rate (MHR) is the 220 minus your age formula. While simple, it's an estimation and can vary significantly between individuals.
Once your MHR is estimated (or measured), the fat burn zone is typically defined as a percentage of this MHR. A widely accepted range for optimal fat burning is between 60% and 70% of your Maximum Heart Rate.
A more personalized calculation, known as the Karvonen formula, also incorporates your Resting Heart Rate (RHR) to determine Heart Rate Reserve (HRR). HRR is the difference between your MHR and RHR. This method provides a more accurate target zone because it accounts for individual fitness levels. The Karvonen formula for the fat burn zone is usually around 50% to 60% of your HRR, added to your RHR.
Fat Burn Zone (Karvonen): (0.50 * HRR) + Resting Heart Rate to (0.60 * HRR) + Resting Heart Rate (if RHR is provided)
Important Considerations:
Listen to Your Body: These are guidelines. Your perceived exertion is also a vital indicator of intensity.
Individual Variation: Maximum heart rate can vary greatly. For precise zones, consider a professional fitness assessment.
Fitness Goals: While the fat burn zone emphasizes fat utilization, higher intensity zones (cardio and peak) burn more total calories per minute, which can also contribute to fat loss overall. A balanced training program often includes various intensities.
Consult a Professional: If you have any health concerns or are new to exercise, consult with a doctor or certified fitness professional.
function calculateFatBurnZone() {
var age = parseFloat(document.getElementById("age").value);
var maxHeartRateInput = parseFloat(document.getElementById("maxHeartRate").value);
var restingHeartRate = parseFloat(document.getElementById("restingHeartRate").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(age) || age = 120) {
resultDiv.innerHTML = "Please enter a valid age between 1 and 120.";
return;
}
var calculatedMaxHeartRate;
if (!isNaN(maxHeartRateInput) && maxHeartRateInput > 0) {
calculatedMaxHeartRate = maxHeartRateInput;
} else {
// Estimate Max Heart Rate using 220 – age formula
calculatedMaxHeartRate = 220 – age;
}
if (isNaN(calculatedMaxHeartRate) || calculatedMaxHeartRate <= 0) {
resultDiv.innerHTML = "Could not calculate maximum heart rate. Please check your inputs.";
return;
}
var fatBurnLowerPercentage = 0.60;
var fatBurnUpperPercentage = 0.70;
// Calculate simplified fat burn zone (60-70% of MHR)
var simplifiedLowerZone = calculatedMaxHeartRate * fatBurnLowerPercentage;
var simplifiedUpperZone = calculatedMaxHeartRate * fatBurnUpperPercentage;
var outputHTML = "
Estimated Maximum Heart Rate: " + Math.round(calculatedMaxHeartRate) + " BPM
";
outputHTML += "Simplified Fat Burn Zone (60-70% of MHR):";
outputHTML += "" + Math.round(simplifiedLowerZone) + " – " + Math.round(simplifiedUpperZone) + " BPM";
// Calculate using Karvonen formula if resting heart rate is provided
if (!isNaN(restingHeartRate) && restingHeartRate > 0 && restingHeartRate < calculatedMaxHeartRate) {
var heartRateReserve = calculatedMaxHeartRate – restingHeartRate;
var karvonenFatBurnLowerPercentage = 0.50;
var karvonenFatBurnUpperPercentage = 0.60;
var karvonenLowerZone = (heartRateReserve * karvonenFatBurnLowerPercentage) + restingHeartRate;
var karvonenUpperZone = (heartRateReserve * karvonenFatBurnUpperPercentage) + restingHeartRate;
outputHTML += "Personalized Fat Burn Zone (Karvonen Formula – 50-60% HRR + RHR):";
outputHTML += "" + Math.round(karvonenLowerZone) + " – " + Math.round(karvonenUpperZone) + " BPM";
} else if (!isNaN(restingHeartRate) && (restingHeartRate = calculatedMaxHeartRate)) {
outputHTML += "Note: Resting Heart Rate input was invalid or too high to calculate the personalized zone.";
}
resultDiv.innerHTML = outputHTML;
}