How heart rate zone calculator works
Your heart rate zones are ranges of beats per minute (bpm) tied to exercise intensity. Training in the right zone targets a specific energy system: Zone 1-2 builds easy aerobic base and fat burning, Zone 3 improves cardio fitness, Zone 4 raises your anaerobic threshold, and Zone 5 develops VO2 max and sprint power. Enter your age (and resting heart rate for the Karvonen method) and the tool maps your personal max heart rate onto five zones.
Max heart rate (HRmax) is estimated from age. The classic Fox formula is 220 minus age. Tanaka (208 minus 0.7 x age) and Gellish (207 minus 0.7 x age) are more accurate, research-backed updates. If you know your measured max from a field test, choose Custom and enter it directly. The estimate is a population average, so your real max can vary by 10-12 bpm.
Two methods convert HRmax into zone ranges. Percent-of-max uses a straight percentage of HRmax (e.g. Zone 3 = 70-80% of HRmax). Karvonen uses heart rate reserve (HRmax minus resting HR) and adds resting HR back, which accounts for your resting fitness and is more accurate for trained individuals. Each zone is then reported as a low-high bpm range you can target during a workout. This is an estimate for education only, not medical advice.
Frequently asked questions
Which max heart rate formula should I use?
Tanaka (208 - 0.7 x age) or Gellish (207 - 0.7 x age) are the most accurate modern formulas for most adults. Fox (220 - age) is the oldest and simplest but overestimates young people and underestimates older people. If you have a measured max from a graded exercise test or a hard field test, choose Custom and enter it.
What is the difference between Karvonen and percent-of-max?
Percent-of-max sets each zone as a straight percentage of your max heart rate. Karvonen (heart rate reserve) subtracts your resting heart rate first, applies the percentage to the reserve, then adds resting back. Karvonen accounts for your resting fitness, so two people with the same max but different resting HRs get different training zones, and is generally preferred for trained individuals.
How are the five zones defined?
Zone 1 is 50-60% (very light recovery), Zone 2 is 60-70% (light, fat burn and base endurance), Zone 3 is 70-80% (moderate aerobic), Zone 4 is 80-90% (hard, anaerobic threshold), and Zone 5 is 90-100% (maximum, VO2 max and sprint work). These are the widely used ACSM-style intensity bands.
Are these heart rate zones accurate for me?
They are research-based estimates, not measurements. Your true max heart rate can differ from the formula by 10-12 bpm, and individual response to training varies. Use the zones as a starting point and adjust based on how a given effort feels (the talk test) and your own test data. For medical or exercise-prescription guidance, consult a qualified trainer or doctor.
