Calculate your training zones based on age, weight, and resting heart rate.
Your Training Profile
Zone
Intensity
BPM Range
Benefit
Estimated Calorie Burn: Based on your weight of kg, training in Zone 3 for 30 minutes burns approximately calories.
Understanding Heart Rate Zones
Heart rate zone training is a method used by athletes and fitness enthusiasts to monitor the intensity of their workouts. By using your age, weight, and resting heart rate (RHR), you can determine the specific beats-per-minute (BPM) ranges that trigger different physiological responses in your body.
The Karvonen Formula
This calculator utilizes the Karvonen Formula, which is considered more accurate than the standard "220-minus-age" method because it accounts for your Resting Heart Rate. This creates a personalized "Heart Rate Reserve" (HRR), representing the actual range your heart can work within.
Zone 1 (50-60%): Very Light. Ideal for recovery, warm-ups, and cool-downs. Improves overall health but doesn't build significant fitness.
Zone 2 (60-70%): Light. The "Fat Burning Zone." This pace should feel comfortable enough to hold a full conversation. It builds basic endurance and aerobic capacity.
Zone 3 (70-80%): Moderate. Aerobic zone. Improves blood circulation and strengthens the heart and skeletal muscles. Conversation becomes difficult.
Zone 4 (80-90%): Hard. Anaerobic zone. You are moving fast and breathing hard. This increases your lactic acid threshold and high-speed endurance.
Zone 5 (90-100%): Maximum. VO2 Max zone. Sprinting or high-intensity intervals. This is for performance peaks and is sustainable only for short bursts.
Why Weight Matters
While heart rate zones are primarily determined by cardiac capacity and age, your weight plays a critical role in energy expenditure. A heavier person requires more energy (calories) to move the same distance or maintain the same heart rate as a lighter person. This is why our calculator provides a weight-adjusted calorie estimate for your moderate training sessions.
Example Calculation
Consider a 35-year-old individual weighing 80kg with a resting heart rate of 65 BPM:
Max Heart Rate: 220 – 35 = 185 BPM.
Heart Rate Reserve: 185 – 65 = 120 BPM.
Zone 2 Lower Limit: (120 * 0.60) + 65 = 137 BPM.
Zone 2 Upper Limit: (120 * 0.70) + 65 = 149 BPM.
function calculateHRZones() {
var age = parseFloat(document.getElementById('hr_age').value);
var weight = parseFloat(document.getElementById('hr_weight').value);
var restingHR = parseFloat(document.getElementById('hr_resting').value);
var resultsDiv = document.getElementById('hr_results');
var tableBody = document.getElementById('zone_table_body');
if (isNaN(age) || isNaN(weight) || isNaN(restingHR) || age <= 0 || restingHR <= 0 || weight <= 0) {
alert('Please enter valid positive numbers for all fields.');
return;
}
// Formulas
var maxHR = 220 – age;
var hrReserve = maxHR – restingHR;
if (hrReserve <= 0) {
alert('Resting Heart Rate cannot be higher than or equal to Max Heart Rate (220 – age).');
return;
}
// Display basic stats
document.getElementById('mhr_display').innerHTML = 'Estimated Max Heart Rate: ' + maxHR + ' BPM';
document.getElementById('weight_ref').innerText = weight;
// Calculate 30-min calorie burn for Zone 3 (approx MET value of 7 for Zone 3)
// Formula: (MET * 3.5 * weight_kg / 200) * minutes
var calories = Math.round((7 * 3.5 * weight / 200) * 30);
document.getElementById('cal_ref').innerText = calories;
// Clear previous results
tableBody.innerHTML = '';
var zones = [
{ name: 'Zone 1', label: 'Recovery', min: 0.50, max: 0.60, benefit: 'Basic health & recovery', color: '#8d99ae' },
{ name: 'Zone 2', label: 'Endurance', min: 0.60, max: 0.70, benefit: 'Fat metabolism & base', color: '#a8dadc' },
{ name: 'Zone 3', label: 'Aerobic', min: 0.70, max: 0.80, benefit: 'Aerobic fitness & stamina', color: '#457b9d' },
{ name: 'Zone 4', label: 'Anaerobic', min: 0.80, max: 0.90, benefit: 'Speed endurance & power', color: '#f4a261' },
{ name: 'Zone 5', label: 'Maximum', min: 0.90, max: 1.00, benefit: 'VO2 Max & peak performance', color: '#e63946' }
];
for (var i = 0; i < zones.length; i++) {
var lowBPM = Math.round((hrReserve * zones[i].min) + restingHR);
var highBPM = Math.round((hrReserve * zones[i].max) + restingHR);
var row = document.createElement('tr');
row.innerHTML = '