This heart rate zone calculator is designed for runners, cyclists, swimmers, and CrossFit enthusiasts who train systematically, dieters targeting the optimal fat-burn range, users of Apple Watch, Garmin, Polar, Wahoo, and Samsung Galaxy Watch, and personal trainers or sports coaches. Enter age and resting heart rate (RHR) to compute maximum heart rate (HRmax) via the Tanaka formula (208 − 0.7 × age, the sports-medicine standard with lower error margins than the traditional formula for adults and seniors) or the classic Fox formula (220 − age). The Karvonen Heart Rate Reserve method then personalizes 5 training zones to your cardiovascular baseline: Zone 1 Recovery (50-60%), Zone 2 Fat Burn (60-70%), Zone 3 Aerobic (70-80%), Zone 4 Anaerobic (80-90%), Zone 5 Max Effort (90-100%). For fat loss, sustaining Zone 2—a conversational pace where you can still speak but slightly out of breath—for 40+ minutes maximizes lipid oxidation. Measure your RHR immediately upon waking while still lying in bed, or use your smartwatch's overnight sleep average for accuracy. If wearable device readings differ, the discrepancy is due to varying manufacturer formulas (Fox vs Tanaka vs Gellish).

• Tanaka Formula: HRmax = 208 - (0.7 × Age)
• Fox Formula: HRmax = 220 - Age
• Karvonen Formula: Target HR = [(HRmax - Resting HR) × Intensity (%)] + Resting HR
• Zone 1: 50-60% | Zone 2: 60-70% | Zone 3: 70-80% | Zone 4: 80-90% | Zone 5: 90-100%