Training Zone Calculator
Calculate your personalized heart rate training zones using the Karvonen or percentage-of-max-HR method. Use it when structuring your weekly runs to target specific fitness adaptations.
Last updated: September 2026
Formula below · 1 source (Wikipedia) · Updated Sep 2026
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About this calculator
Training zones divide your heart rate range into bands, each associated with a different physiological adaptation. The Karvonen method uses your heart rate reserve (HRR = maxHR − restingHR) to set zones relative to your personal range: Zone HR = (maxHR − restingHR) × intensity% + restingHR. This calculator returns the lower boundary of the tempo zone: restingHR + 70% of HRR for Karvonen, or 80% of maxHR for the simpler percentage-of-max method (the two give similar numbers for a typical resting heart rate of about 60 bpm). Tempo running continues up to roughly 80-85% of HRR or about 88-90% of maxHR. If you leave max HR blank, the estimate 220 − age is used; a measured max HR from a hard field test is more accurate, since 220 − age can be off by 10-12 bpm either way. The Karvonen method is generally considered more accurate for individuals with very low or very high resting heart rates, because it anchors zones to your actual heart rate range rather than a population average.
How to use
Example using the Karvonen method: a 35-year-old runner with a resting HR of 55 bpm and no measured max HR. Step 1 - Estimate maxHR: 220 − 35 = 185 bpm. Step 2 - Heart rate reserve: 185 − 55 = 130 bpm. Step 3 - Tempo zone lower bound (70% HRR): 130 × 0.70 + 55 = 91 + 55 = 146 bpm. Step 4 - With the percentage-of-max method instead: 185 × 0.80 = 148 bpm. So this runner's tempo work starts at about 146-148 bpm and runs up to roughly 160-165 bpm near threshold.
Frequently asked questions
What is the difference between the Karvonen method and percentage of max heart rate for training zones?
The percentage-of-max method simply multiplies your maximum heart rate by a fixed percentage (e.g., 70% or 85%) to define zone boundaries, making it quick and easy to apply. The Karvonen method instead uses your heart rate reserve — the range between resting and maximum HR — which means it accounts for individual cardiovascular fitness. For a runner with a low resting heart rate (e.g., 45 bpm), Karvonen zones will be shifted higher relative to max HR compared to percentage-of-max zones, reflecting their greater aerobic capacity. Most exercise physiologists consider Karvonen more individualized and accurate for serious training.
How do I find my maximum heart rate accurately?
The formula 220 − age is a population average with a standard deviation of about 10–12 bpm, meaning it can be off by 20+ bpm for some individuals. The most reliable way to find your true max HR is through a field test: after a thorough warm-up, run several hard intervals at all-out effort and note the highest reading on your heart rate monitor. Lab-based VO2 max tests also record max HR precisely. Once you have a measured value, enter it directly into this calculator to override the age-based estimate and get more accurate training zones.
Why should I train in different heart rate zones rather than always running at the same effort?
Each heart rate zone stimulates a different physiological adaptation. Zone 2 (60–70% max HR) builds aerobic base and fat metabolism efficiency — it is the foundation of endurance. Zone 4 (80–90% max HR) raises your lactate threshold, allowing you to sustain faster paces before accumulating fatigue. Always training at the same moderate effort is a common mistake that leads to a fitness plateau because it never fully stresses either system. Elite runners typically spend 80% of their training in low zones and 20% in high zones, a distribution known as polarized training that has strong evidence behind it.