CalcVitalsTarget Heart Rate Calculator — Karvonen Zones
The Karvonen method personalises training zones with your resting heart rate: target = resting + intensity × (max − resting). For a 30-year-old with a resting rate of 60, training at 70% targets 151 bpm — a very different prescription than a flat percentage of maximum.
How it works
Two people with the same maximum heart rate can need quite different training intensities, and resting heart rate is what separates them: a low resting rate signals a strong, efficient heart with a wide reserve to work in. Karvonen's method (1957) builds zones on that reserve — the gap between resting and max — so the zones land in the right physiological place for the individual, not just the average.
Measure resting heart rate properly or the whole edifice tilts: on waking, lying still, before coffee, phones or standing — ideally averaged across three mornings. Athletes in heavy training blocks sometimes use a resting rate suddenly elevated by 5–10 bpm as an early warning of illness or under-recovery, which is a bonus use of the same measurement.
The zones themselves map to training purposes: Zone 2 builds the aerobic base and is where most endurance volume belongs; tempo and threshold work (Zones 3–4) teach the body to sustain speed; Zone 5 is for short intervals only. If you take one discipline from heart-rate training, make it this: easy days genuinely easy, so hard days can be genuinely hard.
The method
Karvonen: target HR = resting HR + intensity% × (HRmax − resting HR), with HRmax estimated as 220 − age. Zones at 50–60, 60–70, 70–80, 80–90 and 90–100% of heart rate reserve.
Frequently asked questions
Why do my zones differ from my watch's zones?
Most watches default to plain percentage of max (no resting rate) and their own max estimate. Karvonen zones sit a little higher at the same nominal percentage because they start from your resting floor. Neither is wrong — they are different conventions; pick one system and train consistently inside it.
What if I'm on beta blockers or other heart medication?
Then formula zones do not apply — these medicines deliberately blunt heart rate. Train by perceived exertion or the talk test, and take targets from your clinician, not a calculator.
How accurate is 220 − age?
It is a population average with a standard deviation around 10–12 bpm, so your true max may be a full zone away. The max heart rate calculator on this page shows alternative formulas (Tanaka and others) that age more gracefully.