Enter your age and this builds your five training zones. It offers three maximum heart rate formulas, supports the Karvonen heart rate reserve method if you know your resting rate, and shows you how far off the estimate could be — which matters more than most zone calculators admit. Everything runs in your browser and nothing you enter is sent anywhere.
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What heart rate zones actually are
Training zones split the range between rest and maximum effort into bands, each producing a different physiological stress. Easy aerobic work builds endurance through one set of adaptations; hard intervals drive another. Zones are the bookkeeping that stops you doing everything at a moderate intensity and getting the full benefit of neither.
The boundaries themselves are conventions, not biological switches. Nothing measurable happens to you at exactly seventy percent of maximum heart rate. The five-zone model used here is the one most watches and coaches default to, which makes it useful for communication, but the edges should be read as blurry rather than exact.
Which maximum heart rate formula to use
Every zone chart is built on an estimate of your maximum heart rate, so the formula underneath it matters more than the zone percentages do.
220 minus age is the formula nearly every watch and gym poster uses, and it has a considerably weaker foundation than its ubiquity suggests. Robergs and Landwehr traced its history in the Journal of Exercise Physiology Online (2002, 5(2):1-10) and found it was never developed from original research at all — it emerged from an observation across roughly eleven references, some of them unpublished compilations. Their stated conclusion was that the formula has no scientific merit for use in exercise physiology. It is included in the calculator because your watch probably uses it and you may want to see what it produces.
Tanaka (208 − 0.7 × age) is the default here and the better-supported option. Tanaka, Monahan and Seals published it in the Journal of the American College of Cardiology (2001, 37(1):153-156), built from a meta-analysis of 351 studies covering 18,712 subjects and then cross-validated in a laboratory study of 514 people. They reported that the relationship held regardless of sex or habitual activity level, and that 220 minus age underestimates maximum heart rate in older adults.
Gulati (206 − 0.88 × age) was derived specifically in women. Gulati and colleagues published it in Circulation (2010, 122(2):130-137) after stress testing 5,437 asymptomatic women, concluding that the traditional male-derived calculation overestimates maximum heart rate for age in women. Worth noting honestly: Tanaka’s authors reported no sex difference in their own data, so the two findings are not fully reconciled. If you are a woman and the Tanaka zones feel persistently too hard, Gulati is worth trying.
If you have ever seen a genuine maximum during a hard race or a maximal test, use that number instead. A measured maximum beats every formula on this page.
Percent of maximum versus heart rate reserve
The simple method takes percentages straight off your maximum. The Karvonen method, published by Karvonen, Kentala and Mustala in Annales Medicinae Experimentalis et Biologiae Fenniae (1957, 35(3):307-315), works from your heart rate reserve instead: the gap between your resting and maximum rates. Each target becomes your resting rate plus a percentage of that gap.
Reserve-based zones sit higher, and they account for the fact that a well-trained person resting at 45 bpm and an untrained person at 75 bpm are not doing remotely the same work at 130 bpm. If you know your resting rate, it is generally the better choice. Measure it first thing in the morning before getting out of bed, across several days, and take the average.
The Zone 2 confusion
Zone 2 has become shorthand for a specific idea in longevity and endurance circles: training below your first lactate threshold, where fat oxidation is high and the effort is sustainable for hours. That is a physiological definition, and it does not reliably map onto zone 2 in a percentage model.
For a trained endurance athlete the first threshold often sits above seventy percent of maximum heart rate, which means the version of zone 2 discussed on podcasts may land in what this chart calls zone 3. For someone untrained it can sit lower. The two definitions share a name and not a great deal else, which is why people following percentage zones sometimes find their easy days feel implausibly easy.
The practical resolution costs nothing: the talk test. If you can speak in full sentences but would rather not, you are in the right place for aerobic base work, whatever number the watch is showing. If you are choosing words carefully to save breath, you have gone too hard.
When these numbers are wrong
- Individual variation is large. The standard error around age-based estimates is roughly 7 to 11 bpm. That means a substantial minority of people sit outside that band, and some are 20 bpm or more away from the prediction. Your entire zone chart shifts with it.
- Wrist sensors struggle exactly where it matters. Optical readings at the wrist are least reliable during intervals and rapid intensity changes, which is precisely when zone accuracy counts. A chest strap measures electrical activity directly and is materially better for this.
- Heart rate drifts upward. Over a long effort at constant pace, heart rate climbs as core temperature rises and blood volume falls. The same output that reads as zone 2 at minute ten can read as zone 3 at minute ninety.
- Medication changes everything. Beta blockers and some other cardiac medications lower both resting and maximum heart rate. Percentage zones built on an age formula do not apply, and that is a conversation with your doctor rather than a calculator.
- Heat, altitude, caffeine, illness and poor sleep all move heart rate at a given effort. On those days, trust perceived effort over the number on your wrist.
Gear that makes zone training usable
If you intend to train by heart rate rather than glance at it afterwards, a chest strap is the single purchase that changes the quality of your data. The Polar H10 remains the reference device that other monitors get validated against, and it pairs over both Bluetooth and ANT+ so it works with essentially anything. Our full Polar H10 review covers the detail, and our heart rate monitor guide covers the wider field including arm-band options if you dislike chest straps.
For seeing zone distribution across weeks rather than single sessions, a watch that logs and charts time in zone is more useful than a marginally more accurate one-off reading. Our running watch guide and budget running watch guide cover which handle this well. If you are using heart rate to manage training load rather than just intensity, our guide to HRV and overtraining covers the recovery side of the same question.
Frequently asked questions
Should I use Tanaka or 220 minus age?
Tanaka, unless you specifically want to match what your watch displays. It rests on a far larger and better documented dataset. The two happen to agree exactly at age 40. Below that, 220 minus age reads higher: 195 against 191 for a 25-year-old. Above it Tanaka reads higher, and the gap widens with age, reaching 166 against 160 at 60 and 152 against 140 at 80.
How do I find my real maximum heart rate?
The highest reliable figure most people ever see comes from a maximal effort in a race or a supervised test, not from a session where you simply felt tired. It is demanding and carries real cardiovascular risk for anyone with an undiagnosed condition, so it is worth discussing with a doctor first rather than attempting it because a calculator suggested it.
Why are my reserve-based zones higher than my percentage zones?
Because the reserve method starts counting from your resting heart rate rather than from zero. The gap between the two methods widens as resting heart rate rises, so they diverge most for people who are less trained.
Can I train by zones with a wrist-based watch?
For steady efforts, generally yes. For intervals and anything with sharp intensity changes, wrist optical sensors lag and can lock onto your cadence instead of your pulse. If interval precision matters to you, pair a chest strap.
Do my zones change as I get fitter?
Maximum heart rate barely moves with training — it is largely a function of age. What changes is the work you can produce at any given heart rate, and your resting rate, which typically falls. If you use the reserve method, recalculate when your resting heart rate has clearly shifted.