Find your maximum heart rate and five personalised training zones using the Karvonen (heart-rate reserve) method.
The calculator estimates your maximum heart rate with the classic 220 − age formula, then uses the Karvonen method to build your zones: it works from your heart-rate reserve (max HR minus resting HR) rather than raw percentages of max. That makes the zones personal — two 35-year-olds with resting rates of 50 and 75 bpm get meaningfully different targets, as they should, because the fitter heart has more reserve to work with.
Target HR = Resting HR + (Max HR − Resting HR) × intensity%
A 35-year-old with a resting HR of 65 has an estimated max of 185 and a reserve of 120 bpm. Their Zone 2 runs from about 137 to 149 bpm — noticeably higher than the 111–130 bpm a simple percentage-of-max method would suggest, and a better reflection of their actual effort. Measure your true resting HR first thing in the morning, before coffee, for the most accurate zones.
It's a population average with a standard deviation of roughly ±10 bpm, so individual max heart rates vary widely. If you've seen a higher reading during genuine all-out effort, trust that number over the formula — your real zones shift accordingly.
Many devices use simple percentages of max HR, while this calculator uses the Karvonen heart-rate-reserve method, which accounts for your resting rate. Karvonen zones sit higher and are generally considered more personalised, but neither is 'wrong' — just be consistent.
Zone 2 burns the highest proportion of fat per calorie, but higher zones burn more total calories per minute. For most people, overall weekly calorie balance matters far more than the zone itself — pick intensities you can sustain and enjoy.