Heart Rate Zone Calculator

How to use this tool

1. Choose a maximum-HR source. Choose the Classic or Tanaka age estimate, or select measured/custom HRmax and enter a tested maximum. Age is optional when using a measured maximum.
2. Choose a zone method. Select % of maximum HR or Karvonen (% of heart-rate reserve). Your result names both the maximum-HR source and zone method.
3. Enter your age. Enter your age in years for the Classic or Tanaka estimate; it is optional with a measured maximum HR.
4. Add resting heart rate for Karvonen. Resting HR is required and affects results only with Karvonen. If a resting value is entered while % of maximum HR is selected, it is ignored and a notice explains this.
5. View your zones. Your 5 training zones are shown with bpm ranges and training intent.

Understanding training zones

Heart rate zones divide exercise intensity into five bands, each eliciting different physiological adaptations. Training with awareness of your zones helps you structure workouts for specific goals: fat burning, aerobic base building, lactate threshold improvement, or anaerobic power.

Zone descriptions

The intensity percentages use maximum heart rate in the “% of maximum HR” mode. In Karvonen mode, the same percentages apply to heart-rate reserve (HRR), then are added to resting heart rate, so the resulting bpm ranges can differ.

Intensity basis: each percentage is of maximum HR with the % of maximum HR method, or of HRR with Karvonen. Karvonen adds resting HR to that percentage of HRR.

Maximum heart rate estimate

The most common formula is 220 − age. This is a population average with a standard deviation of ±10–12 bpm - meaning your actual max HR could be 20+ bpm different. A more accurate formula (Tanaka, 2001): 208 − (0.7 × age). The only truly direct way to measure maximum HR is a suitable graded exercise test (GXT) or field test. If you have a measured value, choose measured/custom HRmax; age is then optional. For age-based estimates, the calculator rounds maximum HR to the nearest beat before deriving all zone bounds, including Zone 5's upper limit.

Training week structure

Research in endurance sports (particularly running and cycling) supports a 80/20 polarized training distribution for most recreational and competitive athletes:

• ~80% of sessions in Zone 1–2: builds aerobic base with minimal fatigue accumulation.
• ~20% of sessions in Zone 4–5: high-intensity work that drives fitness adaptations.
• Minimize Zone 3: “junk miles” - hard enough to accumulate fatigue but not intense enough to drive the strongest adaptations.

Wearable accuracy

Consumer optical heart rate sensors (Apple Watch, Fitbit, Garmin) are approximately 95% accurate at rest but can show significant error during high-intensity exercise due to motion artifacts. Chest straps (Polar, Garmin HRM) use electrical signals and are considerably more reliable for Zone 4–5 training where precise HR monitoring matters most.

Heart rate reserve (Karvonen) method

The Karvonen formula uses heart rate reserve (HRR) - the difference between your selected maximum HR and resting HR - to define zones relative to resting HR. Choose Classic, Tanaka, or a measured maximum HR separately from the zone method. Resting HR affects the result only when Karvonen is selected:

Target HR = Resting HR + (HRR × Zone %)

For a fit individual with a low resting HR (e.g. 45 bpm), the Karvonen zones sit higher in absolute beats per minute than the simple percentage-of-max method, better reflecting their actual cardiovascular fitness level.