What this calculator measures
Heart-rate training zones define different intensity bands — each eliciting different physiological adaptations. Zone 2 (aerobic base) builds mitochondrial density; Zone 4–5 (threshold and VO2 max) drives aerobic capacity and lactate tolerance. Training across zones in a structured way is more effective than always working at one intensity.
How this calculator works
Maximum heart rate is predicted using the Tanaka formula (208 − 0.7 × age), which is more accurate than the traditional 220 − age formula, particularly for older adults (Tanaka et al., 2001). Zone boundaries are calculated using the Karvonen method: target heart rate = (HRmax − HRrest) × zone% + HRrest. This heart-rate reserve approach produces more personalised zones than methods using HRmax alone.
How to use your result
Measure resting heart rate first thing in the morning over several days and average the readings. Use the zone estimates as planning guides — individual thresholds vary and ideally should be confirmed with a lactate test or structured field test. For most people developing aerobic fitness, spending the majority of cardio time in Zone 2 (conversational effort) is the most effective strategy.
Important limitation
Calculator results are estimates. Pregnancy, eating disorders, medical conditions, injuries, or concerning symptoms require qualified professional guidance.