What this result means
Heart-rate zones are one way to describe intensity. This calculator builds zones from a maximum heart rate you know, or from an age-predicted maximum, and optionally from resting heart rate if you use Karvonen (heart-rate reserve).
Nothing on this page is medical advice, a diagnosis, or a clearance to train. If you take medication that affects heart rate, or you have a heart condition, talk to a clinician.
A 40-year-old with no known max HR has an estimated maximum of 180 bpm using Tanaka (208 − 0.7 × 40). Zone 2 is often 60–70% of max, so about 108–126 bpm on %HRmax. Karvonen zones shift if resting HR is high or low.
If you measured 188 bpm in a true max test, enter 188. Age-predicted max is a population estimate. Individual maximums vary by a wide margin.
Calculation method
Estimated max HR = 208 − 0.7 × age (Tanaka, H., Monahan, K. D., & Seals, D. R., 2001, JACC). Percentage-of-max zones use that maximum. Karvonen uses (max − rest) × percent + rest (Karvonen et al., 1957).
The same inputs always produce the same zones. They still do not know heat, dehydration, or a loose strap.
Age-predicted max HR is often wrong for an individual. Wrist optical sensors lag. Zones are training guidance. They are not a substitute for how the run feels or for clinical care.
Frequently asked questions
How is maximum heart rate estimated?
If you do not enter a known max, this site uses Tanaka: 208 − 0.7 × age. A 40-year-old gets 180 bpm as a population estimate.
What is the Karvonen method?
Heart-rate reserve: (max − rest) × zone percent + rest. It needs a resting heart rate. %HRmax ignores rest.
What is zone 2 heart rate?
On this tool, zone 2 is 60–70% of max (or of reserve, if you use Karvonen). For a 180 bpm max, %HRmax zone 2 is 108–126 bpm.
Is this medical advice?
No. Heart-rate numbers here are for training language only. They are not a diagnosis or a safe-to-exercise certificate.