Core answer: Maximum heart rate ≈ 220 − age (a 40-year-old ≈ 180 bpm); training zones: Zone 1 recovery 50–60%, Zone 2 fat-burning/aerobic 60–70%, Zone 3 tempo 70–80%, Zone 4 threshold 80–90%, Zone 5 max 90–100%. Normal resting HR for adults: 60–100 bpm; athletes 40–60. The more accurate Karvonen method uses heart-rate reserve: target = resting + intensity × (max − resting).
The zone table (age 40, max ≈ 180)
| Zone | % max | bpm | Feels like | Use |
|---|---|---|---|---|
| 1 Recovery | 50–60% | 90–108 | walking easy | warm-up, cool-down |
| 2 Aerobic | 60–70% | 108–126 | can talk in sentences | fat burning, base building |
| 3 Tempo | 70–80% | 126–144 | short phrases | marathon pace |
| 4 Threshold | 80–90% | 144–162 | few words | 10K race effort |
| 5 Max | 90–100% | 162–180 | gasping | intervals, sprints |
Karvonen (heart-rate reserve) — the better formula
HRR = max − resting. A 40-year-old with resting 60: HRR = 120. Zone 2 (60–70% HRR): 60 + 0.6×120 = 132 to 60 + 0.7×120 = 144 bpm — noticeably higher than the naive 108–126, because fitter hearts rest lower. Use Karvonen if you train seriously.
Measuring resting HR correctly
First thing in the morning, before sitting up, 3 mornings averaged. Track trends, not single readings: a +5–7 bpm elevation over baseline suggests incomplete recovery, illness onset, or dehydration — elite coaches use it as a daily go/no-go signal.
Worked examples
Example 1 — Fat-burn zone. Age 30, sedentary: max ≈ 190, zone 2 = 114–133 bpm. A brisk walk or easy cycle holds this; jogging probably overshoots for beginners — that's normal, walk-jog intervals fix it.
Example 2 — The talk test. Free validation: zone 2 = full sentences comfortable; zone 3 = phrases; zone 4+ = single words. No device required, surprisingly accurate.
Example 3 — Warning signs. Resting HR consistently > 100 (tachycardia) or < 40 in non-athletes, or palpitations with dizziness/chest pain → see a doctor, not a calculator.
Common mistakes and myths
- 220 − age is individual — it's a population regression with ±10–12 bpm spread; two 40-year-olds can have maxes of 168 and 192. Field tests (hard 3-min intervals) estimate yours better.
- "Fat-burn zone" misreading — zone 2 burns the highest PERCENTAGE of fat; higher zones burn more TOTAL fat per hour. For weight loss, total deficit rules; zone 2 is sustainable volume, not magic.
- Wrist optical accuracy — wrist HR lags 5–15 s in intervals and fails in cold/dark tattoos; chest straps remain the reference for training.
- Beta-blocker confusion — HR-lowering meds make zone formulas meaningless; use perceived exertion (RPE) instead.
- Chasing max HR — hitting 100% regularly is neither necessary nor wise for recreational athletes; intervals at 85–92% deliver the adaptation.