How does the heart rate zone calculator work?
The tool first estimates maximum heart rate or uses the measured value you enter. It then calculates five percentage bands with either percentage of maximum heart rate or heart-rate reserve.
Traditional maximum HR = 220 − age
Karvonen target HR = resting HR + intensity × (maximum HR − resting HR)
Percent max versus Karvonen
Percentage of maximum multiplies maximum heart rate directly by each intensity percentage. It is simple and does not require resting heart rate.
Karvonen heart-rate reserve subtracts resting heart rate from maximum, applies the percentage to that reserve, and adds resting heart rate back. It changes the zone values according to the individual's resting rate.
Understanding the five zones
The five-zone labels are practical training descriptions, not universal medical definitions. Zone 1 is very easy, Zone 2 is easy steady work, Zone 3 is moderate aerobic work, Zone 4 is hard work, and Zone 5 approaches maximum effort. For running or walking, the pace calculator provides a separate speed and split comparison.
The American Heart Association separately describes moderate activity at about 50%–70% of maximum heart rate and vigorous activity at about 70%–85% of maximum. Those AHA percent-max references are always shown in the result facts.
How to use the heart rate zone calculator
- Enter age and resting heart rate.
- Choose Tanaka, traditional 220-minus-age, or a measured maximum.
- Choose Karvonen heart-rate reserve or percentage of maximum.
- Select Calculate Heart Rate Zones.
- Review all five zones plus the AHA moderate and vigorous reference ranges.
- Use perceived effort and the talk test alongside heart rate.
Accuracy, limitations, and safety
Age-based maximum-heart-rate equations estimate group averages and commonly miss an individual's measured maximum by more than 10 beats per minute. Wrist devices, chest straps, exercise mode, heat, dehydration, caffeine, stress, illness, and medicines can also affect readings; the water intake calculator is only a planning estimate and cannot diagnose hydration status.
People with cardiovascular disease, symptoms, implanted devices, rhythm disorders, or heart-rate-altering medication should ask a qualified clinician for an appropriate exercise target.