Heart Rate Zones: Four Formulas, and Why They Disagree
Training zones are built on a maximum heart rate that almost nobody has actually measured, which makes the estimate underneath them worth understanding. Every formula here is a regression fitted to a population, and individual variation around the fit runs ten to twelve beats either way, which is wide enough to move a zone boundary a whole zone for a given person. This calculator shows four estimates side by side rather than one, and uses the Karvonen method when you supply a resting rate, since that is what makes zones personal rather than generic. Everything runs in your browser.
Table of Contents
Maximum Heart Rate and Its Formulas
It is the highest rate your heart can reach. It falls with age, it is largely genetic, and it is not a measure of fitness. A fitter person does not have a higher maximum, they do more work at every rate below it.
220 minus age was never properly validated. It entered circulation in the 1970s from a rough fit to limited data, and it overestimates young people and underestimates older ones. It remains the most famous formula by a wide margin.
Tanaka came from a meta analysis of 351 studies. Published in 2001, it is generally regarded as the better simple formula and it is the default here for that reason.
Gulati exists because the others were fitted mostly to men. Derived from a study of women specifically, it typically returns a lower figure, and it appears above only for that selection.
How to Use This Calculator
Enter your age and look at the spread. The gap between the four estimates is shown deliberately. If they differ by ten beats, your zones carry at least that much uncertainty before individual variation is added.
Add a resting heart rate. It switches the zones to Karvonen, which works on the range between resting and maximum rather than on maximum alone, and that range is what makes the zones yours.
Enter a measured maximum if you have one. A real figure from a test or from a genuinely maximal effort makes every formula on the page irrelevant, which is the correct outcome.
Treat the boundaries as soft. A beat either side of a zone boundary is not a different kind of training. The zones describe intensities, not thresholds you can cross.
The Karvonen Method
It works on heart rate reserve. The range between resting and maximum, rather than the maximum on its own, which is the range your training actually moves through.
It personalises the zones. Two people with a maximum of 185 and resting rates of 45 and 70 have very different working ranges, and plain percentages of maximum pretend otherwise.
Karvonen zones sit higher. Sixty percent of reserve is a higher figure than sixty percent of maximum, which surprises people comparing the two methods for the first time.
It needs an accurate resting rate. Measured lying still before getting up, ideally averaged over several mornings. A figure taken after coffee and stairs is not a resting rate.
What Each Zone Is For
Zone one is recovery. Genuinely easy, used for warming up and for active recovery between hard days. It should feel almost too slow.
Zone two builds the aerobic base. Conversational, sustainable for hours, and where the majority of endurance training should live. It is also the zone most people skip because it feels unproductive.
Zone three is comfortably hard. Useful in moderation and easy to overuse, because it feels like real training while accumulating fatigue faster than it delivers adaptation.
Zones four and five are the hard work. Threshold intervals raise the pace you can hold for an hour, and maximal efforts develop top end capacity. Both are effective in small doses and damaging in large ones.
Why Most Training Should Be Easy
Elite endurance athletes train easy most of the time. Roughly eighty percent of their volume sits in the low zones, with the remainder genuinely hard.
The middle is the trap. Training that is moderately hard all the time produces enough fatigue to compromise the hard sessions and not enough stimulus to replace them.
Easy has to be actually easy. The most common failure is running easy days at zone three because it feels lazy otherwise, which quietly removes the point of both easy and hard days.
Recovery is when adaptation happens. Training provides the stimulus and rest provides the improvement, which is why more is not reliably better.
Resting Heart Rate as a Signal
Sixty to a hundred is the usual adult range. Trained endurance athletes frequently sit in the forties or lower, which is a normal adaptation rather than a problem.
It falls as aerobic fitness improves. Watching your own figure drop over months is one of the more satisfying and reliable signs that training is working.
A sudden rise is worth noticing. Five to ten beats above your usual morning figure often precedes illness or indicates accumulated fatigue, and it is a good reason to take an easier day.
One reading means little. Caffeine, sleep, stress, alcohol, medication and the time of day all move it. The trend across weeks is the signal.
Measuring Your Real Maximum
A laboratory test is the accurate route. A graded exercise test to exhaustion, supervised, and it is the only way to get a figure you can rely on.
Field tests exist and carry risk. Repeated hard hill efforts can approach the true maximum, and pushing to genuine exhaustion is not something to attempt untrained or unsupervised.
Race data is often close enough. The highest rate seen in the final minutes of a hard race is usually within a few beats of the real figure, and it costs nothing extra.
A chest strap beats a wrist sensor. Optical sensors lag during intervals and can lock onto cadence instead of pulse, which produces confident and completely wrong numbers.
Where Heart Rate Misleads
It lags behind effort. At the start of an interval your heart rate is still climbing while the effort is already maximal, so short intervals are better paced by feel or by power.
Cardiac drift raises it over long sessions. On a long run the same pace produces a steadily higher rate as you dehydrate and heat up, which is not an increase in effort.
Heat, altitude, caffeine and illness all shift it. On a hot day your zone two pace will be considerably slower than usual for the same rate.
Perceived effort remains valuable. A session that feels far harder than the number suggests usually is, and the number is what should be doubted.
Common Mistakes to Avoid
Trusting 220 minus age. It is the least accurate formula in common use, and it is off by the most for exactly the people who use it hardest.
Treating zone boundaries as exact. The estimate underneath them carries ten beats of uncertainty, so a single beat over a boundary means nothing at all.
Training everything in zone three. The most common structural error in endurance training, and it feels like the most productive thing you could be doing.
Using a wrist sensor for intervals. Optical readings lag and sometimes track cadence rather than heart rate, which makes them unsuitable for exactly the sessions where precision matters.
Frequently Asked Questions
Health Disclaimer
These are population estimates, not measurements of your heart. Every formula here carries ten to twelve beats of individual variation, which is wide enough to move a zone boundary substantially for any given person.
Attempting to reach your maximum heart rate is a genuinely maximal effort and carries real risk, particularly if you are untrained, over forty, or have any cardiovascular history. Field testing should not be done alone.
Speak to a doctor before beginning intense exercise, and seek medical attention for chest pain, unusual breathlessness, dizziness, fainting, or a heart rate that is persistently irregular or very high at rest.