Heart Rate Zone Calculator
Calculate your 5 training heart rate zones based on age and resting heart rate for optimal cardio training.
Heart Rate Zones for Smarter Cardio Training
Training without monitoring intensity is like driving without a speedometer — you may be moving, but you have no idea if you are optimizing. Heart rate zones provide a simple, real-time measure of exercise intensity that translates directly into training adaptations. Zone 2 builds aerobic base and fat oxidation efficiency. Zones 4–5 drive VO2 max improvements and lactate threshold gains. Knowing which zone you are in allows you to prescribe your effort rather than guess.
The Karvonen formula, which accounts for resting heart rate, is significantly more accurate than simple max-HR percentages, particularly for well-trained individuals with low resting heart rates. Two people the same age but different fitness levels will have different effective zone ranges using the Karvonen method, reflecting their actual cardiovascular capacity.
The 80/20 rule — spending roughly 80% of training volume in zones 1–2 and 20% in zones 4–5 — is supported by decades of research on elite endurance athletes. The intuitive instinct is to train hard every session, but this produces chronic fatigue and plateaus. The majority of aerobic adaptations occur in lower zones, while high-intensity work provides the intensity stimulus that pushes the ceiling higher.