Your target heart rate (THR) is the beats-per-minute range you should aim to maintain during aerobic exercise to produce a specific training effect. Working within the right zone makes cardio both safe and effective — too low and you get little benefit; too high and you risk overexertion, poor recovery, and accumulated fatigue. This calculator gives you your personalised BPM range for any training goal, together with a full five-zone reference table and calorie-burn projections.
Why heart-rate zones matter
The body fuels movement from three overlapping energy systems. At low intensities (roughly 50-65% of maximum HR) the aerobic system draws heavily on fat oxidation, which is why this band is called the “fat-burning zone.” As intensity climbs toward 65-80%, carbohydrate metabolism takes over and you build cardiovascular endurance — the bread and butter of distance running, cycling, and rowing training. Above 80% you approach the lactate threshold, where lactic acid accumulates faster than it can be cleared; training here raises that threshold and lets you sustain faster efforts. Above 90% is VO2 max territory, the ceiling of aerobic power, improved through short all-out intervals.
Formulas used
Maximum heart rate is estimated from your age using one of four research-backed formulas:
- Fox / Haskell (1970): 220 - age — the classic default, familiar from gym machines
- Tanaka (2001): 208 - 0.7 x age — derived from a meta-analysis of 351 studies; more accurate across the adult lifespan, especially for people over 40
- Gulati (2010): 206 - 0.88 x age — validated in asymptomatic women
- Nes (2013): 211 - 0.64 x age — from a large Norwegian cohort, moderate accuracy
Target zone is then calculated by one of two methods:
- % of Max HR (simple): THR = intensity% x MHR
- Karvonen (heart-rate reserve): THR = HRrest + intensity% x (MHR - HRrest)
The Karvonen method accounts for resting heart rate, so two people with identical ages but different resting HRs (say a trained athlete at 48 bpm versus a sedentary adult at 78 bpm) receive appropriately different zones even though their estimated MHR is the same.
Worked example
A 35-year-old male with a resting HR of 58 bpm and a goal of aerobic endurance training:
- Max HR (Tanaka): 208 - 0.7 x 35 = 183.5 bpm (rounded to 184)
- HR reserve (Karvonen): 184 - 58 = 126 bpm
- Aerobic zone (65-80%): lower = 58 + 0.65 x 126 = 140 bpm; upper = 58 + 0.80 x 126 = 159 bpm
- Calorie estimate (Keytel, 75 kg): at mid-zone (149 bpm) ≈ 11.6 kcal/min, so a 45-minute run burns roughly 522 kcal
| Goal | % range | Karvonen zone | Purpose |
|---|---|---|---|
| Fat / weight loss | 50-65% | 121-140 bpm | Maximal fat oxidation |
| Aerobic endurance | 65-80% | 140-159 bpm | Cardiovascular base |
| Anaerobic threshold | 80-90% | 159-171 bpm | Raise lactate threshold |
| VO2 max / performance | 90-100% | 171-184 bpm | Peak aerobic power |
How to use the results during exercise
Wear a chest-strap heart-rate monitor or a wrist-based optical sensor (chest straps are more accurate, especially above 85% MHR). During steady-state cardio, check your heart rate every 2-3 minutes and adjust pace, resistance, or incline to stay inside the target band. For interval sessions, use the upper bound as your peak target and allow HR to recover to the Zone 1 floor (roughly 50-60% MHR) before the next repetition.
A 10-minute warm-up through Zone 1 before entering your target zone reduces injury risk and helps the cardiac output settle. A similar cool-down prevents blood pooling in the legs.