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Heart Rate Zones Calculator

Calculate your five heart-rate training zones using the Tanaka, Fox, or Karvonen formulas. Pick the method you prefer and get exact bpm ranges for recovery, aerobic, tempo, threshold, and VO2 max work.

Heart rate zone inputs

Karvonen requires a resting heart rate measurement.

This calculator is for informational purposes only and is not a substitute for professional medical advice. Consult a qualified healthcare provider before making changes to your diet, exercise, or health regimen.

What are heart rate zones and why do they matter?

Heart rate zones are bands of exercise intensity defined as a percentage of your maximum heart rate — or, more accurately, as a percentage of your heart rate reserve. Each zone corresponds to a different physiological adaptation: very easy (Z1) for recovery, easy (Z2) for building aerobic capacity and fat oxidation, moderate (Z3) for tempo work, hard (Z4) for raising your lactate threshold, and maximal (Z5) for improving VO2 max. Training in the right zone for your goal is dramatically more effective than training hard all the time.

Heart rate is a cheap, non-invasive proxy for internal load. Unlike pace or power it accounts for heat, sleep, stress, hydration, and terrain — two runs at the same pace can produce very different heart-rate responses, and the higher one is the harder run regardless of what your watch says. Learning to train by heart rate forces honesty about how your body is actually responding.

How this calculator works

The calculator first estimates your maximum heart rate (HRmax) from the formula you pick, then divides that range (or the heart rate reserve, for Karvonen) into five zones according to standard coaching percentages.

  • Fox formula (1971): HRmax = 220 − age. The most famous estimate, easy to remember, but has a large standard deviation (±10–12 bpm) and systematically underestimates HRmax in older adults.
  • Tanaka formula (2001): HRmax = 208 − (0.7 × age). Published in the Journal of the American College of Cardiology, based on a meta-analysis of studies in healthy adults. More accurate across the age range, though still a population average.
  • Karvonen method (1957): target = ((HRmax − HRrest) × intensity%) + HRrest. Rather than applying the percentage to HRmax directly, Karvonen calculates it as a fraction of heart rate reserve, which means the same "zone 2" ends up being different bpm values for a fit person (low resting HR) and an unfit person (high resting HR). This is usually the most useful method for people who know their real resting heart rate.

The five zones use standard percentages from the ACSM Guidelines for Exercise Testing and Prescription: Z1 50–60%, Z2 60–70%, Z3 70–80%, Z4 80–90%, Z5 90–100%.

Worked example

A 40-year-old runner with a resting heart rate of 55 bpm, using the Karvonen method:

  • HRmax (Tanaka, used under the hood by Karvonen here) = 208 − 0.7 × 40 = 180 bpm
  • Heart rate reserve = 180 − 55 = 125 bpm
  • Z2 lower (60% of HRR + rest) = (125 × 0.60) + 55 = 75 + 55 = 130 bpm
  • Z2 upper (70% of HRR + rest) = (125 × 0.70) + 55 = 87.5 + 55 ≈ 143 bpm

Compare that to the plain Tanaka (no HRR) result, which gives Z2 = 108–126 bpm. The Karvonen numbers are higher because they respect the fact that this runner already has a low resting heart rate — Z2 is supposed to be "easy but steady", and 108–126 would be embarrassingly slow for someone with a 55 bpm resting HR.

How to interpret the zones

Each zone has a distinct purpose:

  • Z1 Recovery (50–60%). Active recovery the day after a hard session, or warm-ups and cool-downs. You can hold a normal conversation.
  • Z2 Aerobic (60–70%). The "conversational" pace. Builds mitochondrial density, capillarisation, and fat-burning capacity. Most of an endurance athlete\'s volume should live here.
  • Z3 Tempo (70–80%). "Comfortably hard". Useful for steady-state threshold work but avoid this zone as a default — it is tiring without being stimulating.
  • Z4 Threshold (80–90%). The pace you could hold for a one-hour race. Develops lactate threshold. Use for 20–40 minute intervals.
  • Z5 VO2 max (90–100%). Very hard. Short intervals (30 s to 4 min) with generous recovery. Raises VO2 max, very taxing — once or twice a week max.

Common mistakes

  • Treating 220 − age as gospel. It is a starting estimate with ±10 bpm spread. If you know your actual HRmax from a test or a hard race, use it.
  • Training "grey zone" all the time. Z3 feels productive but drains recovery while delivering less adaptation than pure Z2 or Z4. Spend less time there.
  • Ignoring resting heart rate. If you have a measured resting HR, use Karvonen — it gives more accurate personal zones than the age-based methods.
  • Blindly trusting wrist HR. Optical wrist sensors are often 5–15 bpm off during hard efforts. For intervals, wear a chest strap.
  • Racing your training partner. Heart rate is individual. Someone with a HRmax of 200 and someone with a HRmax of 170 will show very different bpm numbers for the same effort — follow your own zones.
  • Forgetting cardiac drift. On long sessions heart rate slowly creeps up at the same pace because of dehydration and rising core temperature. Hold the zone, not the pace.

When to consult a professional

This calculator assumes a generally healthy adult. It is not appropriate for people taking beta-blockers or other heart-rate-altering medications, people with arrhythmias including atrial fibrillation, anyone under medical care for cardiovascular disease, or pregnant women who have been advised to moderate exercise intensity. If you are over 40 and new to vigorous exercise, have any cardiovascular risk factors (high blood pressure, high cholesterol, diabetes, family history of heart disease), or experience chest pain, dizziness, or abnormal breathlessness during exercise, see a physician and consider a medically supervised exercise stress test before relying on these zones.

Frequently Asked Questions

What are heart rate training zones?
Heart rate zones divide the range between your resting and maximum heart rate into intensity bands (typically five) that correspond to different physiological demands: recovery, aerobic base, tempo, threshold, and VO2 max. Training in the right zone for your goal is one of the most efficient ways to target a specific adaptation — too easy and you get no stimulus, too hard and you accumulate fatigue without the benefit you were chasing.
Which formula should I use: Fox, Tanaka, or Karvonen?
Tanaka (208 − 0.7 × age) is the most accurate of the age-based formulas for healthy adults, with a standard deviation around 10 bpm. Fox (220 − age) is the most famous but consistently underestimates HRmax in older adults and overestimates in younger ones. Karvonen does not estimate HRmax at all — it uses heart rate reserve (HRmax − HRrest) and is the best choice if you know your true resting HR, because it adjusts zones for individual fitness.
How do I find my real resting heart rate?
Measure it first thing in the morning, before getting out of bed, for five consecutive days and take the average. A heart-rate monitor chest strap or wrist tracker is more accurate than counting pulses by hand. Resting HR is lower in fitter individuals (elite endurance athletes can be in the 30s–40s) and higher when you are sick, stressed, or under-recovered, so a sudden 5+ bpm jump is a useful warning sign.
Why do my zones feel wrong?
Age-based HRmax formulas are population averages with a ±10 bpm standard deviation, so about one in three people has a true HRmax more than 10 bpm from the prediction. If Zone 2 feels too easy you may be undershooting your real max; if everything feels impossibly hard you may be overshooting. A maximal fitness test (or a hard race you already did) will tell you your real HRmax, which you can then plug into the calculator manually by picking the age that matches it.
What is Zone 2 training and why is everyone talking about it?
Zone 2 (roughly 60–70% of HRmax, or 60–70% of heart rate reserve with Karvonen) is the "conversational" aerobic pace — fast enough to drive mitochondrial density and fat oxidation, slow enough to accumulate lots of volume without recovery cost. Endurance coaches have prescribed it for decades; recent mainstream attention from physicians like Peter Attia has popularised the idea that 3–4 hours per week of Zone 2 is one of the most durable investments you can make in metabolic health.
How should I split training across zones?
The most commonly recommended distribution for endurance athletes is "80/20 polarised": 80% of training time at Z1–Z2 (easy), 20% at Z4–Z5 (hard), and very little in the Z3 "no mans land". General fitness enthusiasts can get excellent results from two Z2 sessions and one Z4 interval session per week. Runners, cyclists, and rowers all use the same basic framework.
Is it safe to train in Zone 5?
For most healthy adults under 60, brief Zone 5 intervals (30 seconds to 4 minutes) are safe and highly effective for raising VO2 max. They do carry more cardiac risk than easy aerobic work, so people over 40 who are new to intense exercise, anyone with a cardiovascular risk factor (hypertension, high cholesterol, family history, diabetes), and those returning from illness should get a doctor's OK before doing all-out intervals.
Do I need a chest strap or is a wrist monitor good enough?
Wrist-based optical monitors are convenient but can be 5–15 bpm off during high-intensity efforts, especially during lifting or exercises where wrist flexion interferes with the sensor. For easy aerobic work they are usually accurate enough. Chest straps are still the gold standard for intervals and threshold work. If you are serious about training by heart rate, use a chest strap; otherwise, understand that wrist data is a rough guide.
What if I have an irregular heartbeat or take heart medication?
Beta-blockers, some calcium-channel blockers, and other heart medications lower both resting and maximum heart rate. Any age-based HRmax prediction will be wildly wrong for people on these drugs. Atrial fibrillation and other arrhythmias make heart rate monitoring unreliable altogether. Talk to your cardiologist about appropriate training intensities and, in many cases, use perceived exertion (RPE) rather than heart rate.
Is this calculator a substitute for a stress test?
No. A formal exercise stress test performed in a clinic measures your actual maximum heart rate, blood pressure response, and ECG under load, and can detect cardiac abnormalities. The calculator only applies population formulas. Anyone starting a vigorous exercise program over 40 — and anyone of any age with cardiovascular risk factors — should talk to a physician first and consider a medically supervised stress test.