Heart Rate Training Zones
Your 5 personal training zones, computed live with the Karvonen heart-rate-reserve method. Know exactly where to train for each goal.
The 5-zone bands (50/60/70/80/90%) follow the common Polar and British Cycling convention. Karvonen (1957) defined the heart-rate-reserve method, not these specific bands.
The “fat-burning zone” myth
Lower intensity (Zone 2) does burn a higher percentage of calories from fat. But higher intensity burns more total calories, and more total fat. Minute for minute, a Zone 4 effort burns roughly 30% more total calories than Zone 2 (about 1.3 times), and more still once post-exercise burn is counted. For fat loss, total energy expenditure matters most, not the fuel ratio. Zone 2 still builds your aerobic base and aids recovery (Achten & Jeukendrup, 2004, on fat oxidation).
Frequently asked questions
What are heart rate training zones?
Heart rate training zones are ranges of heart rates that correspond to different exercise intensities. There are typically 5 zones, from Zone 1 (light recovery) to Zone 5 (maximum effort). Training in specific zones targets different physiological adaptations: fat oxidation, aerobic endurance, lactate threshold, VO2max, and anaerobic power.
How does the Karvonen method work?
The Karvonen method calculates training zones using Heart Rate Reserve (HRR), the difference between your maximum and resting heart rate. Zone HR = Resting HR + (HRR × target percentage). This is more personal than a simple percentage of max HR because it accounts for your fitness level through resting heart rate.
How accurate is the 220-minus-age formula?
The classic 220-minus-age formula has a standard deviation of about ±10-12 bpm. The Tanaka formula (208 − 0.7 × age) is more accurate, especially for older adults, so this tool uses it. Individual variation is still significant; for precise zones, a graded exercise test or a field max-HR test is best.
Which zone should I train in?
Most endurance athletes follow a polarized model: roughly 80% of training in Zone 1-2 (easy aerobic) and 20% in Zone 4-5 (hard). Zone 3 is the ‘grey zone’ that is often overused. Use the focus buttons above to highlight the zone for your goal.
Learn more
Related tools
- Karvonen MJ, Kentala E, Mustala O (1957). The effects of training on heart rate. Ann Med Exp Biol Fenn, 35:307-315.
- Tanaka H, Monahan KD, Seals DR (2001). Age-predicted maximal heart rate revisited. J Am Coll Cardiol, 37(1):153-156. PubMed
- Achten J, Jeukendrup AE (2004). Optimizing fat oxidation through exercise and diet. Nutrition, 20(7-8):716-727.
- ACSM (2021). Guidelines for Exercise Testing and Prescription, 11th ed. Wolters Kluwer.
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