Calculating Target Heart Rate Zone

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Target Heart Rate Zone Calculator

Your Personalized Training Zones

Based on the Karvonen Formula (includes Resting Heart Rate for higher accuracy).

Note: Your estimated Maximum Heart Rate (MHR) is BPM.
function calculateTHRZones() { var age = parseFloat(document.getElementById('userAge').value); var rhr = parseFloat(document.getElementById('restingHR').value); var resultsDiv = document.getElementById('thrResults'); var zonesOutput = document.getElementById('zonesOutput'); var mhrDisplay = document.getElementById('mhrValue'); if (isNaN(age) || isNaN(rhr) || age <= 0 || rhr <= 0) { alert('Please enter valid positive numbers for both Age and Resting Heart Rate.'); return; } // Calculations var mhr = 220 – age; var hrr = mhr – rhr; // Heart Rate Reserve if (hrr <= 0) { alert('Resting Heart Rate cannot be higher than Maximum Heart Rate (220 – Age).'); return; } var zones = [ { name: 'Zone 1: Very Light (Recovery)', range: [0.5, 0.6], color: '#3498db', desc: 'Improves overall health and helps recovery.' }, { name: 'Zone 2: Light (Fat Burn)', range: [0.6, 0.7], color: '#2ecc71', desc: 'Increases metabolism and aerobic endurance.' }, { name: 'Zone 3: Moderate (Aerobic)', range: [0.7, 0.8], color: '#f1c40f', desc: 'Improves aerobic capacity and cardiovascular strength.' }, { name: 'Zone 4: Hard (Anaerobic)', range: [0.8, 0.9], color: '#e67e22', desc: 'Increases anaerobic capacity and high-speed endurance.' }, { name: 'Zone 5: Maximum (VO2 Max)', range: [0.9, 1.0], color: '#e74c3c', desc: 'Improves maximal sprint power and speed.' } ]; var html = ''; for (var i = 0; i < zones.length; i++) { var low = Math.round((hrr * zones[i].range[0]) + rhr); var high = Math.round((hrr * zones[i].range[1]) + rhr); html += '
'; html += '
' + zones[i].name + '
'; html += '
'; html += '
' + low + ' – ' + high + ' BPM
'; html += '
' + zones[i].desc + '
'; html += '
'; } mhrDisplay.innerHTML = mhr; zonesOutput.innerHTML = html; resultsDiv.style.display = 'block'; resultsDiv.scrollIntoView({ behavior: 'smooth' }); }

Understanding Target Heart Rate Zones

Whether you are a professional athlete or just starting your fitness journey, knowing your target heart rate zone is essential for optimizing your workouts. Heart rate zones help you determine the intensity of your exercise, ensuring you are pushing hard enough to see results without overtraining or risking injury.

The Karvonen Formula: Why It Matters

Most basic calculators simply use the "220 minus age" formula. While simple, it doesn't account for your individual fitness level. This calculator uses the Karvonen Formula, which incorporates your Resting Heart Rate (RHR). By calculating your Heart Rate Reserve (HRR), we can provide a much more accurate window for your training intensity.

Breakdown of Training Zones

  • Zone 1 (50-60%): Ideal for warm-ups, cool-downs, and active recovery. It improves basic circulatory health.
  • Zone 2 (60-70%): Often called the "Fat Burning" zone. At this intensity, your body primarily uses fat for fuel. It is sustainable for long periods and builds endurance.
  • Zone 3 (70-80%): The "Aerobic" zone. This improves your heart and lung capacity. It is the sweet spot for improving cardiovascular fitness.
  • Zone 4 (80-90%): The "Anaerobic" zone. You will feel breathless here. This helps increase your lactate threshold, allowing you to go faster for longer.
  • Zone 5 (90-100%): Maximum effort. Only sustainable for short bursts (sprints). Used mainly for high-intensity interval training (HIIT).

How to Find Your Resting Heart Rate

To get the most accurate results, you should measure your resting heart rate in the morning, immediately after waking up, before you get out of bed. Place two fingers on your wrist (radial pulse) or neck (carotid pulse), count the beats for 60 seconds, or count for 15 seconds and multiply by 4.

Example Calculation

Consider a 40-year-old with a resting heart rate of 60 BPM:

  1. Max Heart Rate: 220 – 40 = 180 BPM
  2. Heart Rate Reserve: 180 – 60 = 120 BPM
  3. Zone 2 Lower Limit: (120 * 0.60) + 60 = 132 BPM
  4. Zone 2 Upper Limit: (120 * 0.70) + 60 = 144 BPM

This individual should aim for 132 to 144 BPM during a steady-state fat-burning run.

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