Heart Rate Zone Calculator
Calculate your five personalised heart rate training zones using either the Karvonen (heart rate reserve) method or the simpler percentage-of-max method. Use it to structure cardio sessions, improve endurance, and avoid overtraining.
About this calculator
Two methods are widely used to define training zones. The simpler percentage-of-max method multiplies maximum heart rate (maxHR) by a zone percentage: zone HR = maxHR × zone_fraction. If maxHR is not measured, it is estimated as 220 − age. The Karvonen method is more precise because it accounts for your resting heart rate (restingHR), using heart rate reserve (HRR = maxHR − restingHR): zone HR = restingHR + HRR × zone_fraction. Zone fractions are approximately: Recovery 0.65, Aerobic 0.75, Threshold 0.85, and VO2max 0.925. The Karvonen method produces higher zone values for fit individuals with low resting heart rates, reflecting their greater cardiovascular efficiency. Both methods use the same zone fractions; only the baseline differs. Accurate maxHR measurement (via a maximal effort test) always outperforms the 220 − age estimate.
How to use
A 35-year-old runner has a resting HR of 55 bpm and wants their aerobic zone using the Karvonen method. Estimated maxHR = 220 − 35 = 185 bpm. HRR = 185 − 55 = 130 bpm. Aerobic zone HR = 55 + 130 × 0.75 = 55 + 97.5 = 152.5 bpm. Using the simpler percentage method: 185 × 0.75 = 138.75 bpm — noticeably lower. The Karvonen result of ~153 bpm is the better target for this athlete. Enter your age, resting HR, preferred method, and training zone to get your personalised figure.
Frequently asked questions
What is the difference between the Karvonen method and the percentage-of-max heart rate method?
The percentage-of-max method simply multiplies your maximum heart rate by a zone percentage, ignoring your fitness level. The Karvonen method instead uses heart rate reserve — the range between your resting and maximum heart rate — and adds a fraction of that reserve to your resting rate. This means two people with identical maximum heart rates but different resting rates (one fit, one sedentary) will receive different zone targets. Because fit athletes tend to have lower resting heart rates, the Karvonen method gives them higher absolute training zone values, which better reflects the effort required to meaningfully stress their cardiovascular systems.
How do I accurately measure my maximum heart rate for heart rate zone training?
The 220 − age formula is a population average with a standard deviation of about 10–12 bpm, meaning it can be significantly off for individuals. A more accurate approach is a maximal effort field test: after a thorough warm-up, perform several hard 1-minute intervals on a hill or track, pushing to all-out effort on the last repetition. The highest value recorded is your practical maxHR. Lab-based VO2max tests with electrocardiogram monitoring are the gold standard. Athletes training seriously should measure maxHR at least once per season, as it changes slowly with age and fitness.
How should I structure weekly training across different heart rate zones?
Most endurance coaches advocate a polarised or pyramidal approach: 75–80% of weekly volume in low-intensity zones (recovery and aerobic), with the remaining 15–20% at threshold or above. High volumes of low-intensity work build the aerobic base — improving fat oxidation, mitochondrial density, and capillary networks — without creating excessive fatigue. Threshold and VO2max sessions provide the stimulus for speed and performance gains. Doing too much work in the moderate 'grey zone' (between aerobic and threshold) accumulates fatigue without the specific adaptation of either extreme. Heart rate monitoring ensures you stay in the intended zone rather than drifting higher.