Heart Rate Zone Calculator

Your five zones come from a single value: your maximum heart rate. The calculator estimates it with Tanaka's formula if you give your age, and uses the real one if you have measured it. Add your resting heart rate and it also gives the zones by heart rate reserve, which are more accurate.

One warning worth more than any zone: a max measured in the field always beats a formula. Every formula describes an average, and nobody is the average.

Why 220 minus age is wrong, and by how much

It's the most widespread formula and the weakest. It was never built as a model: it comes from a line drawn by hand through a scatter of points, in a note from the nineteen-seventies, and it survived because it takes a second to remember.

Its problem isn't being approximate, it's being approximate in a systematic direction. It overstates young adults and understates older ones. At twenty it says 200 when the real average sits around 194. At sixty it says 160 when the real average is closer to 166.

And individual spread stacks on top. Two people of the same age can have max heart rates twenty beats apart with nothing abnormal about either of them. It's a largely genetic trait, and it doesn't improve with training.

Tanaka's formula, 208 minus 0.7 times age, corrects the age-related bias. It doesn't correct individual variability, because no formula can. Hence the ranking: measured first, then Tanaka, and 220 minus age as a last resort.

What each zone actually trains

Zone 1, below 60 percent, is for recovering and moving without paying for it. It's the zone of walking and shakeout jogging. It builds almost nothing and costs almost nothing, which is precisely its use.

Zone 2, 60 to 70 percent, is where most of the volume of a serious plan lives. It's where capillaries and mitochondria get built, the infrastructure that carries everything else. It's also the most misused: nearly everyone runs it too fast.

Zone 3, 70 to 80 percent, is comfortable and deceptive. Hard enough to tire you, not hard enough to force a clear adaptation. Spending your sessions there is the most common way to work a lot and progress little.

Zone 4, 80 to 90 percent, is threshold: the pace you can hold for about an hour. It's the most productive zone per minute spent, and the one to ration.

Zone 5, above 90 percent, only holds for a few minutes. It works the ceiling of the engine, in short repetitions, once a week and no more.

Percent of max, or heart rate reserve

The two columns in the calculator don't say the same thing, and the gap can reach ten beats.

Percent of max is simple: take a fraction of the maximum. Its flaw is ignoring the floor. Someone whose heart sits at 45 at rest and someone at 75 don't have the same room to work with, and the same fraction of maximum doesn't represent the same effort for them.

Heart rate reserve, the Karvonen method, fixes that: you start from resting heart rate and add a fraction of the gap up to maximum. The zones that come out match perceived intensity better, and match oxygen consumption better.

In practice: if you know your resting heart rate, use the Karvonen column. Otherwise the percent-of-max column stays serviceable, with a caveat for hearts that are very slow or very fast at rest.

How to measure your max for real

The protocol fits in a paragraph, and it assumes you're fit, warm and free of any contraindication.

After twenty minutes of progressive warm-up, on a steady hill or a track, run three minutes building the effort and finish flat out over the last minute. Jog three minutes to recover, then do it again trying to go deeper still. The highest number seen across the two repetitions is your max, or very near it.

Two honest remarks. This test needs a chest strap, not a wrist sensor, which drops out exactly when the effort turns maximal. And it doesn't get done if you have any medical doubt, a cardiac history, or are past forty without a check-up: a slightly wrong estimate has never hurt anybody, a badly placed maximal test can.

What heart rate doesn't tell you

This is the part watches stay quiet about.

It drifts. Over a long effort at constant pace it climbs several beats without the intensity changing, purely through fluid loss and rising temperature. After an hour, a zone 2 reads as a zone 3 on screen while the legs are doing exactly what they were.

It reacts to everything else: heat, coffee, a bad night, stress, an infection starting. A morning where it sits ten beats above usual for the same pace isn't progress running backwards, it's information about the state of the day.

It lags. On a thirty-second interval the heart doesn't have time to climb before the effort ends. Steering short intervals by heart rate doesn't work; they get steered by pace or by feel.

Hence a rule worth more than the precision of the zones: on easy sessions, the talk test beats the watch. If full sentences come out, the pace is right, whatever the number says.

The rule that matters more than the zones

You can know your five zones to the beat and still train badly, because the question isn't where the zones sit but how much time you spend in each.

The distribution that works is lopsided: the large majority of volume in zones 1 and 2, a single hard session per week in zone 4 or 5, and as little as possible in zone 3. It's counter-intuitive, and it's what people who progress for years actually do.

The zones are a measuring instrument. The distribution is the decision.

FAQ

Should I use 220 minus age?

As a last resort only. It overstates people under thirty and understates people over fifty, with a systematic bias of five to six beats in each direction. Tanaka, 208 minus 0.7 times age, costs the same effort and gets it less wrong.

How wrong can a formula be?

Two people of the same age can have real max heart rates twenty beats apart. No formula captures that, because it's individual and largely genetic. An estimate is for starting, not for settling anything.

Does my max heart rate drop as I get fitter?

No, and this is a common confusion. Max heart rate declines slowly with age and doesn't move with fitness. What training improves is resting heart rate, which comes down, and how quickly the heart drops back after an effort.

Is a wrist watch good enough?

For easy and moderate efforts, yes, within a few beats. For intervals and for a maximal test, no: the optical sensor drops out on fast changes and on arm movement. A chest strap stays noticeably more reliable where it counts.

Why does my heart rate climb while my pace stays the same?

That's cardiac drift: over a long effort, fluid loss and rising temperature push heart rate up several beats at constant intensity. It isn't a loss of fitness, and it doesn't justify slowing down if the sensations stay good.

Can I run short intervals by heart rate?

No. Over efforts of thirty seconds to a minute, the heart never reaches its working level before the repetition ends. Those sessions get steered by pace or feel, and heart rate gets looked at afterwards, not during.

Which zone burns fat?

None in particular, and this is the most persistent myth in the subject. Total weekly expenditure decides, not the zone of one session. Zones 1 and 2 let you accumulate a lot of volume at a low recovery cost, which makes them useful for that reason and not for a story about fat burning.

Do my zones change as I improve?

The boundaries in beats don't change, since they depend on your max. What changes is the pace you hold inside each zone: at the same heart rate, you go faster. That's exactly how progress reads on a heart rate monitor.

Zones don't make a week

Knowing your zones tells you what intensity to work at. It doesn't tell you how many sessions, which ones, or how to spread them across seven days, and that's where plans come apart. The Vitality Archetype test measures your profile across 5 dimensions in 27 questions and 3 minutes, then generates a week where intensity is dosed for your recovery, with a single hard session when that's what your profile supports. The zones then become sessions, placed on the right days.