Target Heart Rate Calculator
Find your training zones based on age and resting heart rate.
How This Is Calculated
Maximum heart rate is estimated using the common formula 220 minus age. Rather than simply taking percentages of that max, this calculator uses the Karvonen formula, which factors in your resting heart rate too, giving what's often called your "heart rate reserve." This tends to produce more personalized training zones than using max heart rate percentages alone, since it accounts for individual fitness level via resting heart rate. Enter your age and resting heart rate, and all five zones update together.
Why Five Zones Instead of One Target Number
Splitting training intensity into five distinct zones, rather than aiming for one single target heart rate, reflects how different exercise intensities produce different physiological adaptations. Very light and light intensity work primarily builds aerobic base fitness and recovery capacity without significant fatigue accumulation, while moderate intensity improves overall cardiovascular efficiency, and hard and maximum intensities drive improvements in speed, power, and the body's ability to buffer and clear lactate during intense effort. A well-rounded training program typically spends time across several of these zones over the course of a week rather than exclusively targeting just one, which is why the calculator presents the full spread rather than a single recommended number.
What Each Zone Is Typically Used For
- Very Light (50-60%): warm-up, recovery, and easy movement.
- Light (60-70%): fat-burning and base endurance building.
- Moderate (70-80%): cardiovascular fitness and aerobic capacity.
- Hard (80-90%): performance and anaerobic threshold training.
- Maximum (90-100%): short, high-intensity efforts, generally not sustained for long periods.
Worked Example
For a 28-year-old with a resting heart rate of 65 bpm, maximum heart rate is estimated as 220 − 28 = 192 bpm. Heart rate reserve is then max minus resting: 192 − 65 = 127 bpm. Each zone applies its percentage range to that reserve and adds back the resting heart rate. The Very Light zone (50-60%) works out to 127 × 0.5 + 65 = 129 bpm at the low end and 127 × 0.6 + 65 = 141 bpm at the high end, giving a range of 129-141 bpm. Following the same pattern through the remaining zones gives Light at 141-154 bpm, Moderate at 154-167 bpm, Hard at 167-179 bpm, and Maximum at 179-192 bpm, with the top of the Maximum zone equal to the estimated max heart rate itself, since 100% of reserve plus resting heart rate always equals maximum heart rate by definition.
Common Mistakes When Using Heart Rate Zones
A frequent mistake is using an outdated or inconsistent resting heart rate, entering a value measured years ago or during a period of very different fitness level, rather than a recent, consistently measured baseline, which skews every zone calculated from it. Another common mistake is spending too much training time in the Hard or Maximum zones under the assumption that harder is always better, when in reality most evidence-based endurance training approaches recommend the majority of volume happen at lower intensities, with harder efforts used more sparingly and deliberately. A third mistake is treating the estimated maximum heart rate as precise enough to push right up against, given that individual max heart rate can differ from the age-based formula by 10 to 20 beats per minute, training right at the calculated maximum without any margin can mean actually training at or beyond true physiological maximum for some individuals.
The Karvonen Formula's Origin
The formula is named after Finnish physiologist Martti Karvonen, who published research in 1957 proposing that resting heart rate should factor into exercise intensity prescriptions rather than relying on maximum heart rate percentages alone. His key insight was that heart rate reserve, the gap between resting and maximum heart rate, better reflects an individual's actual cardiovascular capacity to increase effort than max heart rate alone does, since two people with identical maximum heart rates but very different fitness levels (and therefore very different resting heart rates) have meaningfully different reserves to work with. This formula remains a standard reference in exercise physiology and sports science education more than six decades after its original publication.
Karvonen Zones vs Simple Max-HR Percentage Zones
Some training programs use a simpler method, taking straight percentages of estimated maximum heart rate without factoring in resting heart rate at all. For the same 28-year-old with a 192 bpm max heart rate, a simple percentage method would put the "Light" zone (60-70% of max) at 115-134 bpm, meaningfully different from the Karvonen-calculated 141-154 bpm for the equivalent reserve-based zone. The gap between the two methods grows for people with lower resting heart rates, since the Karvonen formula shifts zones upward to reflect a wider available reserve, while the simple percentage method treats everyone at the same age identically regardless of fitness level. This is the core practical advantage Karvonen offers over flatter percentage-based approaches.
How to Measure Heart Rate During Exercise
Once training zones are calculated, tracking actual heart rate during exercise is what makes them useful in practice. Chest strap monitors are generally considered the most accurate consumer option, using electrical signals similar to how a medical ECG works. Wrist-based optical sensors, built into most fitness watches and trackers, are more convenient but tend to be somewhat less accurate during high-intensity or highly variable-motion activities, since they infer heart rate from light absorption changes in blood vessels rather than measuring electrical activity directly. Manual pulse checks, counting beats at the wrist or neck for 15 seconds and multiplying by four, are the simplest option but only give a snapshot rather than continuous tracking, making them less practical for staying within a specific zone throughout a workout.
Why Resting Heart Rate Should Be Measured Consistently
Resting heart rate naturally fluctuates somewhat based on sleep quality, hydration, stress, illness, and recent training load, so a single reading taken at an inconsistent time can meaningfully skew the calculated training zones. Measuring first thing in the morning before getting out of bed, ideally averaged across several consecutive days rather than a single reading, gives a more stable and representative baseline. Because the Karvonen formula uses resting heart rate directly in every zone calculation, an unusually high reading (from poor sleep or stress, for instance) would shift every calculated zone upward, potentially prescribing harder-than-intended training intensities on a day when the body may actually need lower intensity or rest.
Frequently Asked Questions
How do I find my resting heart rate?
Check your pulse first thing in the morning before getting out of bed, for a full 60 seconds, ideally over a few days for an average, this is when your heart rate is typically at its lowest natural point.
Why use the Karvonen formula instead of simple percentages?
Simple max-HR percentages don't account for individual fitness differences, while the Karvonen method's use of resting heart rate makes the zones more personalized, someone with a lower resting heart rate (often a sign of better cardiovascular fitness) gets adjusted zones compared to someone with the same age but a higher resting rate.
What exactly is heart rate reserve?
Heart rate reserve is the gap between your estimated maximum heart rate and your resting heart rate, representing the full range your heart rate can move through between complete rest and maximal effort. The Karvonen formula calculates each training zone as a percentage of this reserve added back on top of resting heart rate, rather than as a flat percentage of maximum heart rate alone, which is what makes the zones more individualized.
How accurate is the 220 minus age formula for max heart rate?
It's a widely used population-average estimate, but individual maximum heart rate can vary by roughly 10 to 20 beats per minute from what the formula predicts, even among people of the same age. It was derived from older research using a fairly limited dataset, and more refined formulas have been proposed since, though 220 minus age remains the most commonly cited version due to its simplicity. A supervised maximal exercise test is the only way to measure your actual max heart rate precisely.
Why does a lower resting heart rate lead to different training zones?
A lower resting heart rate is commonly associated with better cardiovascular fitness, since a well-conditioned heart pumps more blood per beat and doesn't need to beat as often at rest. Because the Karvonen formula bases each zone on heart rate reserve (max minus resting), a lower resting heart rate widens that reserve, which shifts the calculated zone boundaries even for two people of identical age and identical maximum heart rate.
Which heart rate zone should I train in most often?
Most endurance training guidelines suggest the bulk of weekly training volume should sit in the Light to Moderate zones (roughly 60-80% of heart rate reserve), with only a smaller portion of training time spent in the Hard or Maximum zones. This pattern, often called polarized or pyramidal training, balances building a large aerobic base with limited higher-intensity work, though specific targets depend heavily on individual goals, sport, and training experience.