Your Heart Rate Zone Calculator
Enter age, resting HR, and optionally a measured max HR
Heart Rate Training Zones — Why Zone 2 Is the Most Important
Heart rate training zones divide your cardiovascular effort into 5 bands, each triggering different physiological adaptations. Understanding your zones allows you to train with purpose — building the right energy systems for your goals, avoiding overtraining, and optimizing recovery.
Zone 2: The Longevity Zone
Zone 2 training (60–70% heart rate reserve) is performed at the upper limit of comfortable aerobic effort — the fastest pace you can sustain while still primarily burning fat and maintaining nasal breathing. It is the cornerstone of endurance training and, increasingly, the cornerstone of longevity-focused health optimization.
At Zone 2 intensity, your body maximally stimulates mitochondrial biogenesis — the creation of new mitochondria. Mitochondria are the energy-producing organelles in every cell; their density and efficiency decline with age and sedentary behavior, driving much of the functional decline associated with aging. Zone 2 training is the most efficient stimulus for reversing this decline. Aim for 3–4 sessions per week of 45–90 minutes in Zone 2 for maximum longevity benefit.
The Karvonen Method vs. Simple % Max HR
The Karvonen formula (Heart Rate Reserve method) is more accurate than simple percentage of max HR because it accounts for your resting heart rate — which reflects your fitness level and autonomic nervous system status. A trained athlete with a resting HR of 45 bpm will have a very different Zone 2 range than a sedentary person with a resting HR of 80 bpm, even if they have identical maximum heart rates.
The most common formula (208 − 0.7 × age) is more accurate than the classic 220 − age but still has a standard deviation of ±7–11 bpm. The only way to truly know your max HR is to measure it during a hard effort — a supervised graded exercise test, or the highest HR recorded during an all-out effort. Many athletes see their true max during sprint intervals or hill repeats at the end of a hard training session.