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).
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 en
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, sma
MHR vs 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 f
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
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