Health & fitness
Target heart rate calculator
Zones based on heart rate reserve account for your resting heart rate, which is why they suit trained and untrained people equally.
Zones
220 minus age is a poor estimate
The familiar formula was never derived from research — it appeared in the 1970s as a rough fit to scattered data and stuck because it is easy to remember. Studies since have found a standard deviation of roughly 10 to 12 beats per minute around it, meaning a substantial share of people are more than 20 bpm away from the figure it gives.
The Tanaka equation, 208 − 0.7 × age, comes from a 2001 meta-analysis and fits observed data better, particularly for older adults where 220 − age underestimates significantly. Both are shown above so you can see the gap.
If you have a genuine maximum from a graded exercise test or a hard race effort, enter it. A measured value beats any equation.
Why Karvonen is the better method
Heart rate reserve is the range you actually have available between rest and maximum. Someone with a resting rate of 45 has a much larger reserve than someone at 75, even at the same age, and the percentage-of-max method ignores that entirely.
The practical consequence is that percentage-of-max sets zones too low for trained people and too high for untrained ones. Karvonen zones come out higher in absolute bpm and correspond more closely to actual perceived effort.
How to measure resting heart rate properly
Take it immediately on waking, before getting out of bed, over several consecutive mornings and average the result. Anything measured after coffee, movement or stress will be elevated. Most wearables track this automatically and their overnight figures are reasonably reliable.
Resting heart rate is also a useful daily signal in itself. A reading five to ten beats above your normal often precedes illness, indicates incomplete recovery from hard training, or reflects poor sleep — and it is one of the simplest early-warning metrics available.
Most training should be easy
Endurance athletes across sports tend to spend roughly 80% of training time in zones 1 and 2 and about 20% at high intensity. The common mistake among recreational athletes is the opposite pattern — most sessions in zone 3, which is hard enough to accumulate fatigue but not hard enough to drive the adaptations that hard intervals produce.
Zone 2 should feel conversational. If you cannot speak in full sentences, you are above it. Many people find their honest zone 2 pace slower than expected, which is normal and not a sign of poor fitness.
Common questions
Are wrist heart rate monitors accurate?
Optical wrist sensors are reasonably good at steady effort and noticeably worse during intervals, weight training and anything involving wrist movement. A chest strap measures the electrical signal directly and is far more accurate for interval work. For zone-based training, a strap is worth the modest cost.
My heart rate goes above my calculated maximum. Is that a problem?
It means the estimate is wrong for you, which is common — the formulas carry a wide error range. Use the highest value you have genuinely seen during hard effort as your maximum instead. If a high rate comes with chest pain, dizziness or unusual breathlessness, stop and see a doctor.
What is cardiac drift?
During prolonged exercise, especially in heat, heart rate rises gradually at constant pace as body temperature rises and blood volume drops. It is normal, and it means heart rate alone will overstate intensity late in a long session. Pace or power is more stable for judging effort over long durations.
Does the fat-burning zone matter?
Lower intensities do use a higher proportion of fat for fuel, but higher intensities burn more total calories and more total fat per minute. For body composition, total energy expenditure and diet matter far more than the fuel mix during a session. Zone 2 is valuable for aerobic development, not because of the fat-burning label.