Heart rate zones answer one question: are you going easy enough to last, or hard enough to change something. The most common way to set them — 220 minus your age — is also the least accurate, and the formula that replaced it is still a population average with a wide individual error. Here are the four methods, what each one gets wrong, the arithmetic worked through, and a ten-minute check that tells you whether your zones are set correctly.
The short answer
If you are not going to test, estimate maximum heart rate with 208 − (0.7 × age), then build the zones on your heart rate reserve — the gap between maximum and resting heart rate. That pairing is the least wrong option available without a lab.
The 208 − 0.7 × age equation comes from a meta-analysis of 351 studies, 492 groups and 18,712 subjects, cross-validated in a laboratory study on a further 514 people, where the regression was virtually identical (209 − 0.7 × age). It did not differ between men and women and was not affected by habitual activity levels (Tanaka, Monahan and Seals, Journal of the American College of Cardiology, 2001).
The same paper carries the caveat almost nobody quotes: the standard deviation around the regression line is roughly 10 beats per minute. For one individual the estimate can be ten beats off in either direction, sometimes more. A zone calculated to the single beat is false precision.
Four methods, compared
| Method | How it works | When it makes sense | The flaw |
|---|---|---|---|
| 220 − age | Straight subtraction | None, once you know the alternative | Underestimates maximum heart rate in older adults — the very problem the 2001 study set out to fix |
| 208 − 0.7 × age | Straight subtraction | Default starting point without a test | Still an average: about 10 bpm standard deviation per person |
| Percentages of reserve (Karvonen) | Zone = resting HR + % × (max HR − resting HR) | When you know your real resting heart rate | Still depends on an estimated maximum, and resting HR has to be measured properly |
| Field test | Measure the highest heart rate reached in a controlled maximal effort | Trained people without contraindications | Requires a genuinely hard effort; unsuitable if you have cardiovascular issues or no base |
The gap between the first two is not academic. At 25 the two formulas nearly agree; at 60 they diverge by several beats, and the old one sends you out training easier than you could.
The arithmetic, worked
Example: 40 years old, resting heart rate measured on waking at 58 bpm.
- Estimated maximum: 208 − (0.7 × 40) = 208 − 28 = 180 bpm.
- Reserve: 180 − 58 = 122 bpm.
- Zones on the reserve: zone = 58 + (percentage × 122).
| Zone | % of reserve | Beats | How it feels | What it is for |
|---|---|---|---|---|
| 1 — very easy | 50-60% | 119-131 | Normal conversation | Active recovery, walking |
| 2 — easy aerobic | 60-70% | 131-143 | Full sentences, no gasping | Aerobic base, most of your volume |
| 3 — moderate | 70-80% | 143-156 | Short sentences | The middle ground: useful in doses, usually overused |
| 4 — threshold | 80-90% | 156-168 | A few words | Tolerance for sustained hard efforts |
| 5 — maximal | 90-100% | 168-180 | No words | Short intervals, low volume |
Had you used percentages of maximum heart rate alone, zone 2 would have been 108-126 bpm: twenty beats lower, a brisk walk instead of an easy run. That is why two apps can give you different zones from the same maximum — they are not disagreeing, they are calculating on different bases. For what to do inside that zone, see the zone 2 training guide.
Measuring resting heart rate without botching it
Take it on waking, before getting up and before coffee, for three or four mornings, then average. A reading taken after lunch at your desk is ten to fifteen beats higher and pushes every zone upward.
If your watch records overnight values, remember the nocturnal minimum is typically lower than a lying-awake reading. Pick one method and stay with it, or you are comparing different numbers over time.
The field test, if you want your own number
It requires a training base, no cardiovascular contraindications and, if in any doubt, clearance from a doctor. It is not a beginner's test and not something to do on a bad day.
- Progressive 15-minute warm-up with two or three strides (structure it with the warm-up guide).
- On a gentle hill or a track: 3 minutes hard but sustainable, 3 minutes easy.
- Repeat the 3-minute block harder, and empty the tank in the final minute.
- The highest value recorded is your maximum estimate, far more reliable than any formula.
Repeat once a year. Maximum heart rate declines slowly with age, not month to month.
When the number on your wrist means nothing
- Medication that acts on heart rate, beta-blockers in particular, lowers both resting and maximum heart rate, so formula-derived zones do not apply. Those references have to be built with a doctor, and perceived effort becomes more useful than the monitor.
- Wrist optical sensors lose accuracy during rapid intensity changes and in cold weather. For short intervals a chest strap gives steadier readings.
- Heat, dehydration, short nights and stress raise heart rate at the same pace — cardiovascular drift. A higher heart rate at your usual pace does not mean you got worse; conditions changed.
- Caffeine shortly before training nudges heart rate up by a few beats.
The ten-minute check that beats any formula
Run or ride twenty minutes in what you believe is zone 2 and try to talk. If you can say a full sentence without breaking the rhythm of your breathing, the zone is right. If you break every three words, you are in zone 3 wearing zone 2's label — the most common error among people who follow only numbers.
The reverse applies at the top: if you can comment on the scenery during a zone 5 interval, the ceiling is set too low. The talk test does not replace measurement; it tells you when the measurement is wrong, and it costs nothing.
What to do with them
Zones are not a programme, they are a speed limit. People who improve usually accumulate a lot of easy volume and a little hard work, not three moderate sessions a week. If your goal is body composition rather than performance, the decision criteria change again: see how much cardio you need to lose fat.
If you come from the weight room: heart rate is a poor intensity gauge under load, because it rises for reasons unrelated to the weight. There the reference is perceived effort, covered in the RPE scale.
FAQ
Which maximum heart rate formula is most accurate? Among age-based formulas, 208 − (0.7 × age) is the strongest: it comes from a meta-analysis of 351 studies and 18,712 subjects and was confirmed in a laboratory sample of 514. But the useful point is not which formula wins. Every age-based estimate carries a standard deviation of about 10 beats, so for any one person it can be ten or more beats off. If you train seriously, one field test a year is worth more than any equation.
Should zones be based on maximum heart rate or heart rate reserve? On the reserve — the difference between maximum and resting heart rate. Using percentages of maximum alone puts the easy zones much lower: in the worked example zone 2 shifts by about twenty beats. That is exactly why two apps can produce different zones from the same maximum. Neither is broken; they use different bases.
Why is my heart rate higher than usual at the same pace? The usual suspects are heat, dehydration, poor sleep, stress, caffeine and digestion, plus incomplete recovery from a previous session. Five to ten extra beats for a day or two is not a problem. If it persists for a week alongside fatigue, worse sleep and declining performance, look at your overall load and the signals described in the guide to overtraining symptoms.
Do heart rate zones apply to lifting? Not usefully. Under load, heart rate rises from the isometric component, breath-holding and incomplete recovery rather than in proportion to the weight lifted. A heavy triple can push your heart rate as high as an easy run while being a completely different stimulus. For resistance training, use perceived effort or a percentage of your maximum.
Do I need to recalculate every year? Yes, but no more often. Maximum heart rate falls by roughly half a beat to a beat per year of age, so nothing meaningful changes month to month. Resting heart rate moves faster as your condition improves, and it is worth rechecking every two or three months because it shifts every zone built on the reserve.
Where to start
Calculate your zones with the reserve method, then check zone 2 with the talk test in your next session: if the two disagree, trust your breathing and correct the numbers. If you want those values stored alongside your sessions instead of in a scattered spreadsheet, Athleex keeps your workouts, progress and measurements in one place, and shares them with your coach automatically if you train with one.
Source checked on 19 September 2026: Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol 2001;37(1):153-156. doi:10.1016/S0735-1097(00)01054-8. Stated limits: healthy adults, group-level equation with about 10 bpm standard deviation for individuals; not applicable to people taking medication that alters heart rate.