Heart Rate Zones
Karvonen reserve zones built on Tanaka rather than the familiar but less accurate '220 minus age'.
- 01Enter your age and sex.
- 02Add a resting heart rate if you have one — measured on waking, averaged over several days.
- 03Optionally add a Cooper test distance (12 minutes of maximal running) for a VO₂ max estimate.
What the terms mean
- Max HR
- The highest heart rate you can reach during maximal effort.
- Resting HR
- Your heart rate on waking, before getting up. Falls as fitness improves.
- HR reserve
- The gap between resting and maximum heart rate.
- Karvonen
- A zone method using heart rate reserve, so zones reflect your conditioning.
- VO₂ max
- The maximum rate at which your body can use oxygen.
Resting heart rate switches the calculation to the Karvonen method, which accounts for your conditioning. Measure it on waking, before getting up.
Distance covered in a 12-minute maximal run, for a VO₂ max estimate.
Estimated with Tanaka · zones use the Karvonen reserve method.
VO₂ max estimated via Resting/max heart rate.
Method & sources
"220 − age" (Fox) is the familiar formula but overestimates in younger adults and underestimates in older ones. Tanaka is better validated across age groups, so it is used here. Any max-HR formula carries roughly ±10 bpm of individual variation — a real maximal test is the only precise answer.
Tanaka H et al., J Am Coll Cardiol 2001 · Karvonen MJ et al. 1957 · Gulati M et al., Circulation 2010 · Cooper KH, JAMA 1968
What these numbers
actually tell you.
Why the zones move when you add resting heart rate
Without it, zones are a flat percentage of maximum, which ignores the bottom of your range. Karvonen sets them from the gap between resting and maximum instead, so two people with the same max but very different fitness get appropriately different zones. The shift can be twenty to thirty beats.
These boundaries carry about ten beats of uncertainty
Any age-based max-HR estimate has substantial individual variation — two people the same age can genuinely differ by twenty beats. Tanaka is used here because it is better validated than "220 minus age", which overestimates in younger adults and underestimates in older ones. Only a real maximal test gives a precise figure.
The practical use is keeping easy days easy
Trained endurance athletes accumulate most volume at low intensity with a small amount genuinely hard. The common recreational error is the opposite — too much moderately hard work, which builds fatigue without delivering either the aerobic adaptation of easy volume or the stimulus of real intervals. Zone 2 is the one most people skip.
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