Target Heart Rate Calculator
Percent-of-maximum zones are a rough guide. The Karvonen method, which factors in your resting heart rate, gives you zones that reflect your own fitness.
The Karvonen method
The simple approach takes a percentage of maximum heart rate. The problem is that it ignores where your heart rate starts from. Karvonen's method uses heart rate reserve — the working range between rest and maximum — which makes the zones personal:
Consider two 40-year-olds with the same estimated maximum of 180 bpm. One has a resting rate of 75 bpm, the other 50 bpm after years of training. At 70 % intensity the first should be at 149 bpm, the second at 141 bpm. A plain percent-of-max calculation gives both 126 bpm and under-prescribes for both.
Estimating maximum heart rate
Every formula here is a population average with a standard deviation of roughly ±10–12 bpm. For an individual that is a wide margin, and it is the main weakness of any zone calculation.
- 220 − age is the famous one. It was never derived from research; it was an informal approximation from the 1970s that stuck. It systematically overestimates for the young and underestimates for older adults.
- Tanaka (2001): 208 − 0.7 × age came from a meta-analysis of 351 studies and is the better general-purpose default.
- Gulati (2010): 206 − 0.88 × age was derived specifically in women, where the classic formula performs worst.
If it matters to you, a supervised maximal test or a hard, well-paced race effort will give a real number that beats any estimate.
What each zone trains
| Zone | % HRR | Feels like | Trains |
|---|---|---|---|
| 1 Recovery | 50–60 | Easy conversation | Active recovery, blood flow |
| 2 Aerobic base | 60–70 | Full sentences | Mitochondria, capillaries, fat oxidation |
| 3 Tempo | 70–80 | Short sentences | Aerobic capacity, lactate clearance |
| 4 Threshold | 80–90 | A few words | Lactate threshold, race pace |
| 5 VO₂ max | 90–100 | No talking | Maximal oxygen uptake, top-end power |
Most endurance athletes follow a roughly 80/20 distribution: about 80 % of training time in zones 1 and 2, and 20 % in zones 4 and 5. The classic amateur mistake is living in zone 3 — too hard to build an aerobic base efficiently, too easy to drive adaptation at the top end.
The so-called “fat burning zone” around 65 % is real but widely misread. You do burn a higher proportion of fat at low intensity, but a smaller total number of calories. For fat loss, total energy expenditure and diet dominate.
Frequently asked questions
Why is my watch's max heart rate different?
Most devices default to 220 − age unless you set a tested value. If you have ever recorded a higher heart rate than your estimate during a hard effort, that recorded figure is the better number — put it in your device settings.
Is it dangerous to reach my maximum heart rate?
For a healthy person cleared for vigorous exercise, briefly reaching maximal effort is normal and safe. If you have cardiovascular disease, uncontrolled blood pressure, or symptoms such as chest pain, dizziness or unusual breathlessness, get medical clearance before high-intensity work.
Should I use heart rate or perceived effort?
Both. Heart rate lags effort by a minute or two, drifts upward during long sessions, and is pushed around by heat, caffeine, dehydration, illness and poor sleep. On a day when your heart rate is 10 bpm above normal at an easy pace, trust how you feel.