Training zones organize effort into intensity ranges so an easy aerobic session does not accidentally become a hard workout. This calculator compares age-based maximum-heart-rate estimates, including the Tanaka equation, and can use the Karvonen heart-rate-reserve method when a resting heart rate is supplied. Seeing more than one estimate helps explain why different watches and training plans may show different boundaries.
Heart rate is affected by heat, hydration, fatigue, stress, medication, altitude, illness, and sensor quality. Use zones as guidance alongside perceived effort and the purpose of the session. A chest strap may respond more quickly during intervals than a wrist sensor, and anyone with a cardiac condition or medication that changes heart rate should obtain individualized advice before relying on generic targets.
Zones can be based on a percentage of estimated maximum heart rate or on heart rate reserve, which includes resting heart rate. The latter can personalize the range when the resting measurement is reliable.
Tanaka is a population-based alternative that may reduce average estimation error for some adults, but neither formula knows your tested maximum. Use the result as a starting point and compare it with observed effort.
Zone 2 generally describes a sustainable aerobic effort where conversation remains possible. Exact boundaries vary by method, fitness, and sport, so breathing and perceived exertion are useful checks alongside the displayed range.
Heat, dehydration, poor sleep, stress, illness, fatigue, caffeine, and medication can all affect heart rate. Stop and seek medical advice for concerning symptoms such as chest pain, faintness, or unusual breathlessness.