Heart rate zones are ranges of beats per minute (bpm) that group exercise intensity into practical training bands. Instead of treating every workout simply as easy or hard, zones make it easier to compare sessions, plan recovery, and describe the main physiological demand of a workout.
Most consumer fitness apps use a five-zone model. The exact boundaries vary by platform, coach, and sport, but a common starting point is to express each zone as a percentage of maximum heart rate.
| Zone | % of max HR | Intensity | Typical use |
|---|---|---|---|
0 | <50% | Rest | Rest and everyday movement below purposeful training intensity. |
1 | 50-60% | Very easy | Warm-ups, cool-downs, recovery work, and easy movement that should feel conversational. |
2 | 60-70% | Easy aerobic | Steady endurance work where breathing is controlled and sustainable for a long time. |
3 | 70-80% | Moderate aerobic | Tempo-like aerobic work that still feels controlled, but requires more focus. |
4 | 80-90% | Hard | Threshold work and harder intervals where speaking becomes difficult. |
5 | 90-100% | Very hard | Short maximal or near-maximal efforts with limited repeatability. |
How Heart Rate Zones Are Determined
The most accurate way to set zones is to measure your own physiology, usually with a supervised maximal exercise test, a lactate threshold test, or a carefully run field test. In practice, many people start with an age-based estimate and then adjust it when they have better data from a hard workout, lab test, or coach.
The key input is maximum heart rate (max HR): the highest bpm you can reach during maximal effort. Age-based formulas estimate it for a population, but they can be wrong for an individual by enough to shift zones noticeably. If you know your measured max HR, use that instead of an age formula.
Estimating Max Heart Rate
The classic estimate is:
A commonly used alternative is the Tanaka equation:
Most basic formulas only use age. Gender or sex-specific formulas exist, such as formulas developed for women, but they are still estimates. Fitness level, medication, stress, sleep, heat, hydration, altitude, illness, and sensor accuracy can all affect observed heart rate. Body weight alone is not normally used to estimate max HR. See Estimating Max HR for a detailed comparison of the most common equations.
Calculating Zones From Max HR
Once max HR is known or estimated, percentage-based zones are calculated by multiplying max HR by each zone boundary.
Example: a 40-year-old using the classic formula has an estimated max HR of 180 bpm. Zone 2 at 60-70% would be 108-126 bpm.
Heart Rate Reserve Method
A more personalized method uses heart rate reserve, sometimes called the Karvonen method. It accounts for resting heart rate, so two people with the same max HR can receive different training ranges.
Example: with a max HR of 180 bpm and resting HR of 60 bpm, heart rate reserve is 120 bpm. Zone 2 at 60-70% HRR would be 132-144 bpm.
Heart Rate Zone Categories
For workout summaries, the dominant zones can be grouped into broader categories. Use the category that best describes where most of the meaningful work occurred, not necessarily the single highest zone touched for a few seconds.
| Category | Dominant Zones |
|---|---|
| Rest | 0 |
| Recovery | 1 |
| Low Intensity | 1 2 |
| Aerobic | 2 3 |
| Mixed / Intervals | 2 3 4 |
| High Intensity | 4 5 |
Practical Notes
- Use measured max HR to determine heart rate zones when available; age formulas are only starting points.
- Keep the calculation method consistent when comparing workouts over time.
- Review zones after major fitness changes, a birthday if using age-based estimates, or a verified new peak HR.
- Be cautious with zones if you take medication that affects heart rate or have a cardiovascular condition.
Sources
Useful references include:
- Target Heart Rate Guide by American Heart Association
- Exercise Intensity Guidance by Mayo Clinic
- Heart Rate Reserve Explanation by Cleveland Clinic