What heart rate zones actually are
Heart rate zones are five intensity bands, each defined as a percentage of your maximum heart rate, that show how hard your cardiovascular system is working during exercise: Zone 1 (50-60%) is recovery, Zone 2 (60-70%) builds aerobic base and burns fat, Zone 3 (70-80%) is steady aerobic, Zone 4 (80-90%) is your threshold, and Zone 5 (90-100%) develops VO2 max. Training by zone lets you match effort to purpose, so an easy day stays genuinely easy and a hard day is actually hard. To turn these percentages into real numbers you first need an estimate of your maximum heart rate, and then, if you want a more personal result, your resting heart rate.
This is general information, not medical advice. If you have a heart condition, take medication that affects heart rate (such as beta blockers), or are new to exercise and over about 40, talk to a clinician before pushing into the higher zones.
Estimating your maximum heart rate
Your maximum heart rate (HRmax) is the highest number of beats per minute (bpm) your heart can reach during all-out effort. It is largely set by age and genetics and falls slowly as you get older. Short of a lab test or a maximal field test, you estimate it with a formula.
220 minus age (the classic)
The best-known rule is HRmax = 220 - age. For a 40-year-old that gives 180 bpm. It is simple and fine as a starting point, but it was never derived from rigorous research and it tends to overestimate HRmax in younger adults and underestimate it in older adults.
Tanaka: 208 - 0.7 x age (more accurate for older adults)
A 2001 analysis by Tanaka and colleagues, pooling data from 351 studies and more than 18,000 people, produced HRmax = 208 - (0.7 x age). Its flatter slope diverges from the classic formula at the ends of the age range. A 25-year-old gets about 190 bpm by Tanaka versus 195 by the classic rule; a 60-year-old gets about 166 bpm by Tanaka versus 160 by the classic rule. In middle age the two nearly agree (both land at 180 bpm at age 40). For older adults especially, Tanaka is the better estimate.
Why any estimate is a starting point
Every age formula describes a population average, not you. Real individual maximums scatter roughly 10-12 bpm above or below the predicted line, and some people differ by 20 bpm or more. That means your true Zone 4 could sit noticeably higher or lower than a chart suggests. Use the estimate to set up your zones, then refine them using how you actually feel and, over time, data from real workouts. The quickest way to convert either formula into your five zones is our find your zones tool.
The five zones and what each one trains
Here is what each band feels like and why you would spend time there. Percentages are of maximum heart rate.
- Zone 1 - 50-60% (Recovery): Very easy. Walking, warm-ups, cool-downs, and easy days between hard sessions. Promotes blood flow and recovery without adding fatigue. You can talk or sing freely.
- Zone 2 - 60-70% (Aerobic base / fat burning): Comfortable, conversational effort you can hold for a long time. This zone builds the aerobic engine, improves your body's ability to use fat for fuel, and is where endurance athletes spend most of their hours. It should feel almost too easy.
- Zone 3 - 70-80% (Aerobic): Steady, moderately hard tempo work. Talking becomes short sentences. It improves aerobic efficiency, but done constantly it can become a fatiguing grey zone: too hard to recover from, too easy to drive top-end gains.
- Zone 4 - 80-90% (Threshold): Hard, sustained effort near the point where lactate starts to accumulate faster than you can clear it. Talking is limited to a few words. This raises the pace you can hold before fatigue sets in.
- Zone 5 - 90-100% (VO2 max): Maximal or near-maximal intervals lasting seconds to a few minutes. This develops peak oxygen uptake and top-end power. It is demanding and should be a small, carefully placed part of training.
The Karvonen method: more personal targets
The simple percent-of-max method ignores your resting heart rate, which reflects your fitness. The Karvonen method (the heart-rate-reserve method) fixes that. First find your heart rate reserve (HRR):
- HRR = HRmax - resting heart rate
- Target = (HRR x intensity%) + resting heart rate
Take a 40-year-old with an estimated HRmax of 180 bpm and a resting heart rate of 60 bpm. Their HRR is 120. At 70% intensity, Karvonen gives (120 x 0.70) + 60 = 144 bpm, whereas the plain percent-of-max method gives 126 bpm. Karvonen targets sit higher and, because they factor in your resting heart rate, they are more individual: two people the same age but at different fitness levels get different zones. Measure your resting heart rate first thing in the morning, before getting up, for the most reliable figure.
How intense should you go? The AHA range and 80/20 idea
For general health, the American Heart Association points most people toward a training range of 50-85% of maximum heart rate: about 50-70% for moderate activity and 70-85% for vigorous activity. That maps neatly onto Zones 1 through 4. Beginners should start near the bottom of the range and build up gradually. This aligns with public-health targets from the WHO and CDC of 150-300 minutes of moderate, or 75-150 minutes of vigorous, aerobic activity per week, plus muscle-strengthening on two or more days.
If your goal is endurance performance rather than general fitness, a useful principle from the research of Stephen Seiler and others is 80/20 training: spend about 80% of your sessions easy (Zones 1-2) and only about 20% hard (Zones 4-5), with little time in the middle. Elite athletes across running, cycling, rowing, and skiing converge on this pattern. The common amateur mistake is running easy days too hard, drifting into the grey zone and blunting recovery, so the hard days cannot be hard enough. To connect these efforts to real running speeds, pair your zones with our pace calculator to see the pace each zone should feel like.
| Zone | % of max HR | Primary purpose |
|---|---|---|
| Zone 1 - Recovery | 50-60% | Warm-up, cool-down, active recovery |
| Zone 2 - Aerobic base | 60-70% | Endurance base, fat utilisation, easy volume |
| Zone 3 - Aerobic | 70-80% | Steady tempo, aerobic efficiency |
| Zone 4 - Threshold | 80-90% | Raise the sustainable hard pace |
| Zone 5 - VO2 max | 90-100% | Peak oxygen uptake, top-end power |
Five-zone model as a percentage of estimated maximum heart rate. These are conventional endurance-training bands; your personal zones may sit slightly higher or lower once you account for real HRmax and resting heart rate.
Safety for beginners, older adults, and cardiac patients
Zone targets are guides, not orders. A few sensible cautions:
- Beginners: Start in Zones 1-2, where you can hold a conversation, and let higher zones come after a few weeks of consistent aerobic work. Sharp chest pain, dizziness, or unusual breathlessness means stop.
- Older adults: The Tanaka estimate is usually the better fit, and individual scatter matters more, so favour how you feel over the exact number. Build volume before intensity.
- Cardiac patients and people on heart-rate-lowering medication: Beta blockers and similar drugs cap and lower heart rate, which throws off every formula. Zones should be set by a clinician or cardiac-rehab team, often from a supervised exercise test, not from an online chart.
- Everyone: Heat, illness, dehydration, caffeine, stress, and poor sleep all push heart rate up at a given effort. On those days, ease off rather than chasing a number.
Putting it together
Estimate your HRmax (Tanaka is a good default, especially past 40), decide whether you want simple percent-of-max zones or the more personal Karvonen targets, and anchor most of your training in easy Zones 1-2 with a smaller dose of harder Zone 4-5 work. Recheck your zones a few times a year, since resting heart rate and fitness shift. As your aerobic fitness improves, a natural next step is to see how that translates to a goal event with our race time predictor, which turns a recent result into a realistic target time.
Key sources: Tanaka, Monahan & Seals (2001), "Age-predicted maximal heart rate revisited," Journal of the American College of Cardiology (meta-analysis of 351 studies, 18,712 subjects); Karvonen, Kentala & Mustala (1957) on heart rate and training; American Heart Association target heart rate guidance (50-85% of max); WHO Guidelines on Physical Activity and Sedentary Behaviour (2020) and CDC adult activity guidelines; ACSM's Guidelines for Exercise Testing and Prescription; Seiler and colleagues on intensity distribution (80/20) in endurance athletes. Formulas give population averages; individual maximum heart rate scatters roughly 10-12 bpm around any estimate.