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.
Why 220 minus age is the wrong formula
The familiar 220-minus-age rule has no strong research basis and carries a wide margin of error — often ten beats per minute or more for an individual. It systematically underestimates maximum heart rate in older adults.
The Tanaka equation, 208 minus 0.7 times age, was derived from a large meta-analysis and predicts maximum heart rate more accurately across the adult age range. This calculator uses it, then applies Karvonen percentages to your heart-rate reserve so your resting heart rate shapes the zones too.
How much time to spend in each zone
Most endurance programmes keep the large majority of weekly volume easy, in zones 1 and 2, with a small share of hard work at higher intensity. Going moderately hard on every session tends to produce fatigue without the adaptations of either extreme.
For general health, 150 minutes of moderate activity per week is the common public-health target. For aerobic base building, 120 to 180 minutes per week in zone 2 across two to four sessions is a practical starting structure.
Important limitation
Calculator results are estimates. Pregnancy, eating disorders, medical conditions, injuries, or concerning symptoms require qualified professional guidance.