Heart Rate Zones Calculator
Calculate your 5 heart rate training zones using either the simple age-based method or the more accurate Karvonen formula (which uses your resting heart rate).
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Why Heart Rate Zones Matter?
Different intensities trigger different training adaptations. Heart rate is one of the most accessible measures of intensity. Training in specific zones for specific durations builds specific fitness components. Without zones: most untrained exercisers default to medium intensity — too hard to fully recover, too easy to drive significant adaptation. The 'no-man's land' of training. With zones: structured intensity distribution. 80% easy + 20% hard (polarised) is the dominant model among elite endurance athletes and coaches, since it maximises aerobic base fitness while still allowing enough hard, high-quality sessions to drive performance gains.
What should I know about Calculating Max HR?
Methods vary in accuracy: 220 - age (Fox formula, 1971): widely cited, surprisingly inaccurate. Underestimates by 5-10 bpm for those over 40. 208 - 0.7 × age (Tanaka, 2001): more accurate across age range. Slightly higher max HRs predicted. 206 - 0.88 × age (Gulati, 2010): for women specifically — even higher than Tanaka. Karvonen, Astrand variants: similar concept. Why formulas vary: individual variation is huge. Two people same age can have max HR 30+ bpm apart. Genetics, training history, smoking, and fitness level all play a role, which is why a real field or lab test gives a far more reliable number than any age-based formula.
What's the difference between MHR and HRR (Karvonen) Method?
Max Heart Rate method (MHR): zones calculated as % of max HR. 60% of 185 max HR = 111 bpm. Simple. Used by most fitness trackers (Apple Watch, Garmin default). Heart Rate Reserve (HRR / Karvonen): zones calculated using both max AND resting HR. Target HR = Resting + (% × HRR). Where HRR = Max - Resting. Example: 35yo, resting 60, max 185. HRR = 125. Zone 2 (60%) = 60 + (0.60 × 125) = 135 bpm. MHR method: same person, Zone 2 (60% max) = 111 bpm. 24 bpm lower. Which is more accurate? HRR adjusts for individual resting heart rate, giving a more personalised zone calculation than a simple percentage of max heart rate alone.
What do I need to know about The Five Zones Explained?
Zone 1 (50-60% MHR / 50-60% HRR): recovery. Easy conversation. Active recovery between hard sessions. Less than 10% of training time. Zone 2 (60-70% / 60-70%): aerobic base. Can hold full conversation. 60-80% of total training time for endurance athletes. Drives aerobic adaptation, capillarisation, mitochondrial density. The 'forgotten' zone — most amateur athletes spend too little time here. Maffetone method (180 - age, similar to upper Z2): popular long-form fat-burning training. Zone 3 (70-80): tempo/threshold work — challenging but sustainable for 20-60 minutes. Zone 4 (80-90) and Zone 5 (90-100+) cover harder interval and maximal efforts, used sparingly given the recovery demands they place on the body.