Train at the right intensity
Running, cycling or swimming by feel often means going too hard on easy days and not hard enough on hard ones. Heart rate zones give you objective targets for every session. This calculator estimates your maximum heart rate, your heart rate reserve, your five training zones and a target heart rate at any intensity you choose.
These values are estimates for general fitness. Before starting high-intensity training, especially over 40 or with heart disease risk factors, check with your doctor.
The formulas
Maximum heart rate:
- classic: 220 − age;
- Tanaka: 208 − 0.7 × age, more accurate for adults over 40;
- or your measured value from an exercise test.
Heart rate reserve = max HR − resting HR.
Karvonen method: target HR = resting HR + intensity × heart rate reserve.
Worked example: age 40, resting heart rate 62 bpm
- Max HR (Tanaka): 208 − 0.7 × 40 = 180 bpm.
- Heart rate reserve: 180 − 62 = 118 bpm.
- Zone 2 (60%): 62 + 0.6 × 118 ≈ 133 bpm.
- Zone 3 (70%): 62 + 0.7 × 118 ≈ 145 bpm.
- Zone 4 (80%): 62 + 0.8 × 118 ≈ 156 bpm.
- Zone 5 (90%): 62 + 0.9 × 118 ≈ 168 bpm.
The five zones
| Zone | Intensity (reserve) | How it feels | Purpose |
|---|---|---|---|
| 1 | 50–60% | very easy | recovery, warm-up |
| 2 | 60–70% | easy conversation | aerobic base, fat oxidation |
| 3 | 70–80% | steady, short sentences | tempo, marathon pace |
| 4 | 80–90% | hard | lactate threshold intervals |
| 5 | 90–100% | all-out | VO₂ max intervals, sprints |
Many endurance coaches recommend spending roughly 80% of training time in zones 1 and 2 and 20% in zones 3 to 5.
Max heart rate and zones by age (resting HR 62 bpm)
| Age | Max HR (Tanaka) | Zone 2 starts | Zone 4 starts |
|---|---|---|---|
| 20 | 194 bpm | 141 bpm | 168 bpm |
| 30 | 187 bpm | 137 bpm | 162 bpm |
| 40 | 180 bpm | 133 bpm | 156 bpm |
| 50 | 173 bpm | 129 bpm | 151 bpm |
| 60 | 166 bpm | 124 bpm | 145 bpm |
| 70 | 159 bpm | 120 bpm | 140 bpm |
Fine-tuning your zones
Age formulas can be off by 10 beats or more. If your zones do not match how hard sessions feel (out of breath in zone 2, or zone 4 feels easy), your real max is probably different. A supervised exercise stress test, or a carefully paced field test once you are already fit, gives a better number. Re-check your resting heart rate every couple of months: it drops as your fitness improves.
What else affects heart rate
Heat, dehydration, poor sleep, stress, caffeine, altitude and medications such as beta blockers all change your heart rate at the same effort. Wrist-based optical sensors are also less accurate than a chest strap during hard intervals, so compare readings before relying on them.