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Evidence-based health calculators to estimate Body Mass Index (BMI), U.S. Navy body fat percentage, Karvonen heart rate zones, daily calorie expenditure (TDEE), and optimal daily hydration.
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10/24/2026Heart Rate Training Zones
Heart Rate Training Zones
Calculate Karvonen target heart rate zones (Zones 1-5) and max heart rate based on age and resting HR.
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Heart Rate & Training Zones
Years of age
Measure right after waking up (average: 60-75 bpm)
5 Heart Rate Training Zones (Karvonen Method)
Zone 1: Very Light / Active Recovery125 – 137 BPM
50% – 60% Heart Rate ReserveWarming up, cooling down, recovery, builds aerobic foundation without fatigue.
Zone 2: Light / Aerobic & Fat Burn137 – 149 BPM
60% – 70% Heart Rate ReserveLong endurance rides/runs, conversational pace, maximizes mitochondrial density & fat oxidation.
Zone 3: Moderate / Aerobic Tempo149 – 161 BPM
70% – 80% Heart Rate ReserveTempo workouts, steady state, improves cardiovascular efficiency and blood circulation.
Zone 4: Hard / Lactate Threshold161 – 173 BPM
80% – 90% Heart Rate ReserveInterval training, race pace, builds high-speed endurance and raises anaerobic threshold.
Zone 5: Maximum / Neuromuscular173 – 185 BPM
90% – 100% Heart Rate ReserveShort all-out sprints (15-60s), peak power and anaerobic capacity. Straining.
Heart Rate Key Metrics
Estimated Maximum Heart RatePeak Cap
185BPM
Using Fox standard (220-age)
Resting HR65 BPM
Heart Rate Reserve120 BPM
Recommended Training Distribution
Polarized 80/20 Training: Most endurance athletes and exercise scientists recommend spending roughly 80% of workout time in Zone 1 & Zone 2 (aerobic base), and 20% in high-intensity Zones 4 & 5.
Zone 2 training improves fat oxidation and mitochondrial efficiency without overstressing the nervous system, enabling faster recovery between hard workouts.