How to Calculate Heart Rate Zones by Age

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Heart Rate Zone Calculator

Zone 1: Very Light (50-60%)
Warm-up, recovery, and active regeneration.
Zone 2: Light (60-70%)
Base endurance building and fat metabolism.
Zone 3: Moderate (70-80%)
Aerobic fitness improvement and steady-state pace.
Zone 4: Hard (80-90%)
Anaerobic capacity and speed endurance.
Zone 5: Maximum (90-100%)
Sprints and short-term peak performance.

How to Calculate Heart Rate Zones by Age

Understanding your heart rate zones is the key to training smarter, not harder. By monitoring your heart rate during physical activity, you can ensure you are working at the right intensity to meet your specific goals—whether that is burning fat, increasing endurance, or improving your maximum athletic performance.

The Formula for Maximum Heart Rate (MHR)

The foundation of all heart rate zone calculations is your Maximum Heart Rate. The most common and simple formula used by fitness professionals is the Fox Formula:

Max Heart Rate (MHR) = 220 – Age

For example, if you are 40 years old, your estimated maximum heart rate would be 180 beats per minute (BPM).

The 5 Heart Rate Zones Explained

Fitness zones are typically divided into five categories based on a percentage of your MHR:

  • Zone 1 (50-60%): Very light intensity. Great for warming up or cooling down.
  • Zone 2 (60-70%): Light intensity. This is the "fat-burning zone" where your body primarily uses fat for fuel.
  • Zone 3 (70-80%): Moderate intensity. Improves your cardiovascular system and aerobic capacity.
  • Zone 4 (80-90%): Hard intensity. You begin to work anaerobically, building speed and power.
  • Zone 5 (90-100%): Maximum effort. Only sustainable for very short bursts, usually used in HIIT or sprinting.

Advanced Method: The Karvonen Formula

While the basic formula works for many, the Karvonen Formula is often more accurate because it takes your Resting Heart Rate (RHR) into account. This calculates your Heart Rate Reserve (HRR).

The math follows this sequence:

  1. 220 – Age = Max HR
  2. Max HR – Resting HR = Heart Rate Reserve (HRR)
  3. (HRR × % Intensity) + Resting HR = Target Heart Rate

Example Calculation (Age 30, Resting HR 60)

  • Max HR: 220 – 30 = 190 BPM
  • HRR: 190 – 60 = 130 BPM
  • Zone 2 (60% Lower Bound): (130 × 0.60) + 60 = 138 BPM

Why Monitoring Zones Matters

Without knowing your zones, it is easy to "overtrain" in the "gray zone"—where you are working too hard to recover properly but not hard enough to see significant aerobic gains. By using a calculator to establish your specific ranges, you can target your workouts to burn fat efficiently or peak for a race.

function calculateHRZones() { var age = parseFloat(document.getElementById('userAge').value); var rhr = parseFloat(document.getElementById('restingHr').value); if (isNaN(age) || age 120) { alert("Please enter a valid age."); return; } var mhr = 220 – age; document.getElementById('mhrDisplay').innerText = "Your Max Heart Rate: " + mhr + " BPM"; var useKarvonen = !isNaN(rhr) && rhr > 30 && rhr < 150; function getRate(percent) { if (useKarvonen) { var hrr = mhr – rhr; return Math.round((hrr * percent) + rhr); } else { return Math.round(mhr * percent); } } // Zone 1: 50-60% document.getElementById('z1Range').innerText = getRate(0.50) + " – " + getRate(0.60) + " BPM"; // Zone 2: 60-70% document.getElementById('z2Range').innerText = getRate(0.60) + " – " + getRate(0.70) + " BPM"; // Zone 3: 70-80% document.getElementById('z3Range').innerText = getRate(0.70) + " – " + getRate(0.80) + " BPM"; // Zone 4: 80-90% document.getElementById('z4Range').innerText = getRate(0.80) + " – " + getRate(0.90) + " BPM"; // Zone 5: 90-100% document.getElementById('z5Range').innerText = getRate(0.90) + " – " + mhr + " BPM"; document.getElementById('hrResults').style.display = 'block'; }

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