Why are my watch zones different?

Wearables may use different maximum heart rate formulas, lactate-threshold testing, recent workout data, or proprietary zone labels. The important part is being consistent with one method and adjusting when you have better measured data.

Is Zone 2 always 60% to 70%?

This tool uses a common five-zone model. Some coaches define Zone 2 with lactate, ventilatory threshold, power, pace, or slightly different percentages, so trained athletes may need sport-specific testing.

Is any health information stored?

No. The calculator runs locally in your browser. Age, resting heart rate, and optional max heart rate entries are not sent to a server by this tool.

Heart Rate Zone Calculator

Calculate target exercise heart rate zones from age, resting heart rate, optional measured max heart rate, and training method.

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Last updatedJuly 11, 2026How we build & check our tools

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How This Tool Works

The calculator turns your age, resting heart rate and (optionally) a measured maximum heart rate into five training zones. If you leave the maximum blank, it estimates it with the Tanaka equation, max HR = 208 - 0.7 x age, which comes from a meta-analysis of 351 studies (18,712 people) and tracks measured values more closely than the older 220 - age rule, especially for older adults.

It then offers two ways to set the zones:

Percent of maximum heart rate: each zone is a percentage band of max HR (Zone 1 = 50-60%, Zone 2 = 60-70%, Zone 3 = 70-80%, Zone 4 = 80-90%, Zone 5 = 90-100%).
Heart rate reserve (Karvonen method): the same percentages are applied to your reserve, max HR minus resting HR, and resting HR is added back: target = resting + % x (max - resting). Because it accounts for your baseline, it places the zones higher for people with a low resting heart rate.

All results are rounded to the nearest beat per minute, and the calculation runs entirely in your browser.

Worked Example

Take the default inputs: age 40 and a resting heart rate of 64 bpm, with no measured maximum. The estimated maximum is 208 - 0.7 x 40 = 180 bpm, so the heart rate reserve is 180 - 64 = 116 bpm.

Zone 2 with heart rate reserve: 64 + 0.60 x 116 = 133.6, and 64 + 0.70 x 116 = 145.2, shown as 134-145 bpm.
Zone 2 with percent of max: 0.60 x 180 = 108 and 0.70 x 180 = 126, shown as 108-126 bpm.
Zone 4 with heart rate reserve: 64 + 0.80 x 116 = 156.8 to 64 + 0.90 x 116 = 168.4, shown as 157-168 bpm.

The two methods can differ by 20 bpm or more in the easier zones, which is why it matters to pick one method and stay consistent with it.

Limitations and Sources

Any age-based formula is an average: an individual's true maximum can be 10 bpm or more above or below the estimate. A supervised exercise test or a hard field test gives a better number. Beta blockers and some other medications, caffeine, heat, dehydration, illness and altitude all change exercise heart rate. This tool is for general fitness planning, not medical advice. If you have a heart condition or take heart-rate-lowering medication, ask your doctor for target ranges, and stop exercising and seek help for chest pain, fainting or severe breathlessness.

Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. Journal of the American College of Cardiology. 2001;37(1):153-156.
Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate: a longitudinal study. Annales Medicinae Experimentalis et Biologiae Fenniae. 1957;35(3):307-315.
U.S. Centers for Disease Control and Prevention. Target Heart Rate and Estimated Maximum Heart Rate (moderate activity at about 50-70% and vigorous activity at about 70-85% of maximum).

Frequently Asked Questions

Common questions about the Heart Rate Zone Calculator

Use percent of maximum heart rate when you only know your age or measured max. Use heart rate reserve when you also know a reliable resting heart rate; it personalizes the zones by accounting for your lower baseline.

Sources & References

Health reference data

Authoritative public-health reference data and definitions from the U.S. CDC.

→Source: U.S. Centers for Disease Control and Prevention

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