Calculate your target heart rate zones to maximize fat burning.
General
Male
Female
Leave blank for standard formula. Enter for Karvonen accuracy.
Your Estimated Maximum Heart Rate (MHR)
— BPM
Target Fat Burning Zone (60% – 70%): —
Zone
Intensity
Heart Rate Range (BPM)
Primary Benefit
How Heart Rate Affects Weight Loss
Understanding your Maximum Heart Rate (MHR) is crucial for optimizing your workouts, specifically when your goal is weight loss. Your body utilizes different energy sources depending on the intensity of your exercise. By training in specific "zones," you can dictate whether your body burns predominantly carbohydrates (glycogen) or stored body fat.
The "Fat Burning" Zone Explained
The term "Fat Burning Zone" typically refers to a low-to-moderate intensity aerobic exercise where your heart rate stays between 60% and 70% of your maximum heart rate. In this zone, the body relies more heavily on fat oxidation for fuel compared to higher intensity zones.
Zone 1 (50-60%): Very light activity, warm-up/cool-down. Aids recovery.
Zone 2 (60-70%): The "Fat Burning Zone." Improves general endurance and metabolizes fat efficiently. This is ideal for long, steady-state cardio sessions.
Zone 3 (70-80%): Aerobic zone. Improves cardiovascular fitness and stamina. You burn more total calories here, but a lower percentage comes from fat.
Zone 4 & 5 (80-100%): Anaerobic/Peak zones. Used for HIIT (High-Intensity Interval Training). While the percentage of fat burned is lower during the activity, the "afterburn" effect (EPOC) can keep metabolism elevated for hours.
Calculation Methods Used
This calculator utilizes two primary methods depending on the data you provide:
Fox Formula (220 – Age): The standard method used globally for a quick estimation of maximum heart rate.
Karvonen Method: If you input your Resting Heart Rate (RHR), the calculator uses the Heart Rate Reserve (HRR) formula. This is considered more accurate for individuals with varying fitness levels because it accounts for the difference between your resting and maximum heart rate.
Safety Precautions
While heart rate training is an effective tool for weight loss, always consult with a healthcare professional before starting a new exercise regimen. The numbers provided here are estimates. Factors such as medications (like beta-blockers), stress, caffeine, and hydration can influence your actual heart rate.
function calculateHeartRateZones() {
// 1. Get Inputs
var ageInput = document.getElementById('calc_age');
var genderInput = document.getElementById('calc_gender');
var rhrInput = document.getElementById('calc_rhr');
var resultDiv = document.getElementById('mhr_results');
var age = parseFloat(ageInput.value);
var gender = genderInput.value;
var rhr = parseFloat(rhrInput.value);
// 2. Validate Inputs
if (isNaN(age) || age 100) {
alert("Please enter a valid age between 10 and 100.");
return;
}
// 3. Calculate MHR (Maximum Heart Rate)
// Standard formula: 220 – Age
// Gulati formula for women: 206 – (0.88 * Age) (Optional refinement, but sticking to standard variations for clarity)
// Tanaka: 208 – (0.7 * Age)
var mhr = 0;
// Using a hybrid approach for better accuracy
if (gender === 'female') {
// Gulati formula is often cited as better for women
mhr = 206 – (0.88 * age);
} else {
// Standard Fox formula
mhr = 220 – age;
}
mhr = Math.round(mhr);
// 4. Calculate Zones
// We calculate lower and upper bounds for 5 zones: 50-60%, 60-70%, 70-80%, 80-90%, 90-100%
var zones = [];
var methodUsed = "";
// Check if RHR is provided for Karvonen Method
if (!isNaN(rhr) && rhr > 30 && rhr < 120) {
methodUsed = "Karvonen Method (Uses Heart Rate Reserve for higher accuracy)";
var hrr = mhr – rhr; // Heart Rate Reserve
// Formula: (HRR * intensity) + RHR
zones = [
{ name: "Zone 1: Very Light", percent: "50% – 60%", min: Math.round((hrr * 0.50) + rhr), max: Math.round((hrr * 0.60) + rhr), benefit: "Warm up / Recovery" },
{ name: "Zone 2: Light (Fat Burn)", percent: "60% – 70%", min: Math.round((hrr * 0.60) + rhr), max: Math.round((hrr * 0.70) + rhr), benefit: "Max Fat Burning / Endurance" },
{ name: "Zone 3: Moderate", percent: "70% – 80%", min: Math.round((hrr * 0.70) + rhr), max: Math.round((hrr * 0.80) + rhr), benefit: "Aerobic Fitness" },
{ name: "Zone 4: Hard", percent: "80% – 90%", min: Math.round((hrr * 0.80) + rhr), max: Math.round((hrr * 0.90) + rhr), benefit: "Anaerobic Threshold" },
{ name: "Zone 5: Maximum", percent: "90% – 100%", min: Math.round((hrr * 0.90) + rhr), max: mhr, benefit: "Maximum Performance" }
];
} else {
methodUsed = "Standard Method (Percentage of Max Heart Rate)";
// Standard Percentage Method
zones = [
{ name: "Zone 1: Very Light", percent: "50% – 60%", min: Math.round(mhr * 0.50), max: Math.round(mhr * 0.60), benefit: "Warm up / Recovery" },
{ name: "Zone 2: Light (Fat Burn)", percent: "60% – 70%", min: Math.round(mhr * 0.60), max: Math.round(mhr * 0.70), benefit: "Max Fat Burning / Endurance" },
{ name: "Zone 3: Moderate", percent: "70% – 80%", min: Math.round(mhr * 0.70), max: Math.round(mhr * 0.80), benefit: "Aerobic Fitness" },
{ name: "Zone 4: Hard", percent: "80% – 90%", min: Math.round(mhr * 0.80), max: Math.round(mhr * 0.90), benefit: "Anaerobic Threshold" },
{ name: "Zone 5: Maximum", percent: "90% – 100%", min: Math.round(mhr * 0.90), max: mhr, benefit: "Maximum Performance" }
];
}
// 5. Update UI
document.getElementById('display_mhr').innerHTML = mhr + " BPM";
document.getElementById('calc_method_note').innerHTML = "Calculation Method: " + methodUsed;
// Update Fat Burn Highlight
var fatBurnZone = zones[1]; // Index 1 is Zone 2
document.getElementById('display_fat_burn_range').innerHTML = fatBurnZone.min + " – " + fatBurnZone.max + " BPM";
// Build Table
var tableBody = document.getElementById('zone_table_body');
tableBody.innerHTML = ""; // Clear previous results
for (var i = 0; i < zones.length; i++) {
var row = document.createElement('tr');
var z = zones[i];
// Highlight Zone 2 (Fat Burn)
if (i === 1) {
row.className = "highlight-row";
}
row.innerHTML =
"
" + z.name + "
" +
"
" + z.percent + "
" +
"
" + z.min + " – " + z.max + "
" +
"
" + z.benefit + "
";
tableBody.appendChild(row);
}
// Show Results
resultDiv.style.display = "block";
// Scroll to results
resultDiv.scrollIntoView({behavior: 'smooth'});
}