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Heart Rate Zones

Training in the right heart rate zone determines whether you're burning fat, building aerobic base, or improving speed. The five-zone model (developed by exercise physiologists and used by Garmin, Polar, and Whoop) divides intensity from light recovery to maximum anaerobic effort. Our calculator uses your max heart rate and resting HR to compute your personal zones.

Max Heart Rate:

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About the Heart Rate Zone Calculator

Training in the right heart rate zone determines whether you're burning fat, building aerobic base, or improving speed. The five-zone model (developed by exercise physiologists and used by Garmin, Polar, and Whoop) divides intensity from light recovery to maximum anaerobic effort. Our calculator uses your max heart rate and resting HR to compute your personal zones.

How to use it

  1. Enter your age to auto-calculate estimated max HR (220 − age), or enter your measured max HR.
  2. Enter your resting heart rate for Karvonen formula zones (more precise).
  3. See all five zones: Zone 1 (recovery), Zone 2 (fat burn/base), Zone 3 (aerobic), Zone 4 (threshold), Zone 5 (max).
  4. Choose the training goal that matches your current focus.

Formula & methodology

Estimated max HR (HRmax) = 220 − age (±10–12 bpm). Karvonen (HRR method): Target HR = ((HRmax − HRrest) × intensity%) + HRrest. Zone 1: 50–60% HRmax. Zone 2: 60–70%. Zone 3: 70–80%. Zone 4: 80–90%. Zone 5: 90–100%. Lactate threshold typically near top of Zone 3 / bottom of Zone 4.

Common use cases

  • Endurance training: building aerobic base in Zone 2 (80% of training volume)
  • Fat loss: Zone 2 maximizes fat oxidation percentage per calorie burned
  • Race preparation: lactate threshold intervals in Zone 4
  • Recovery runs: staying in Zone 1–2 on easy days
  • VO2max development: Zone 5 intervals for peak fitness

Frequently asked questions

Zone 2 (60–70% max HR) builds mitochondrial density and fat oxidation capacity — the aerobic engine that powers everything else. Elite endurance athletes spend 70–80% of their training volume in Zone 2. Training too hard too often (the classic "moderately hard all the time" mistake) blunts Zone 2 adaptations and increases injury risk. Easy days should be genuinely easy.
It's a rough estimate with ±10–12 bpm variability — meaning a 40-year-old's real max HR could be anywhere from 168 to 192. For serious training, measure your actual max HR: a 20-minute all-out running effort or a lab VO2max test. The Karvonen formula using measured resting HR improves zone accuracy even without knowing true max HR.

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