Heart Rate Zone Calculator

Nearly every heart rate zone on your watch is a percentage of one number: your maximum heart rate. Get that number wrong and every zone underneath it is wrong too. This calculator estimates your max with the formula that actually holds up in the research, then splits it into five training zones two ways. The first is a straight percentage of your max. The second is the Karvonen heart rate reserve method, which factors in your resting heart rate to personalize each zone to your fitness.

The default here is the Tanaka et al. 2001 equation, not the familiar 220 minus age. That older shorthand was never validated as a prediction tool, a story we cover in depth in our research review of max heart rate formulas. You can still select it, clearly labeled as legacy, but Tanaka, Gulati, and Nes all describe real bodies better.

How this calculator works

Every formula and boundary in this tool comes from a primary source. Nothing is invented.

• Max heart rate (default): the Tanaka et al. 2001 equation in the Journal of the American College of Cardiology, 208 minus 0.7 times age. It was pooled from 18,712 subjects across 351 studies and separately validated on 514 healthy adults. It tracks lab-measured max better than 220 minus age across the lifespan.
• Max heart rate (women): the Gulati et al. 2010 equation in Circulation, 206 minus 0.88 times age. Built from 5,437 women in the St. James Women Take Heart Project, it corrects the overestimate that male-anchored formulas produce for women.
• Max heart rate (active adults): the Nes et al. 2013 HUNT Fitness Study equation in the Scandinavian Journal of Medicine & Science in Sports, 211 minus 0.64 times age. Measured in 3,320 recreationally active Norwegian adults.
• Max heart rate (legacy): 220 minus age. Included only because people expect it. Robergs and Landwehr 2002 showed it traces to a 1971 graph that was never tested as a prediction equation, with a standard deviation of 7 to 12 bpm.
• Zones by percent of max: Zone 1 is 50 to 60 percent, Zone 2 is 60 to 70 percent, Zone 3 is 70 to 80 percent, Zone 4 is 80 to 90 percent, and Zone 5 is 90 to 100 percent. These are the standard five-zone boundaries used across mainstream endurance training.
• Karvonen zones (heart rate reserve): when you enter a resting heart rate, the calculator switches each zone to the Karvonen et al. 1957 method. Target heart rate equals ((max heart rate minus resting heart rate) times the intensity) plus resting heart rate. This personalizes zones to your fitness, since a lower resting heart rate widens your usable reserve.

What is a good max heart rate by age?

There is no single good number. Max heart rate is a structural ceiling set by your physiology, not a fitness score, and it drifts down slowly with age. Using the Tanaka formula, a 20-year-old averages about 194 bpm, a 30-year-old about 187, a 40-year-old 180, a 50-year-old 173, and a 60-year-old 166. Those are averages. Two healthy people of the same age can differ by 20 beats. A higher or lower max does not mean you are fitter or less fit, it just means your ceiling sits where it sits.

The important caveat is error. Shookster and colleagues (2020) measured true max in 99 adults and found the individual error stayed near 10 beats per minute regardless of the formula. So treat the number as a center point with a wide band around it, not a precise target.

What heart rate is Zone 2?

Zone 2 is the one everyone asks about, and for good reason. It is the aerobic base zone, sitting at 60 to 70 percent of max, where most of your endurance adaptations happen. For a 40-year-old with a max of 180, that is about 108 to 126 bpm by percent of max. Layer in a resting heart rate of 60 with the Karvonen method and Zone 2 lifts to roughly 132 to 144 bpm. It should feel genuinely easy, the kind of pace where you can hold a conversation. If you are gasping, you have drifted into Zone 3. We go deeper on why this zone matters in our guides on the science of Zone 2 training and doing Zone 2 cardio at home.

Is 220 minus age accurate?

Not really. It is easy to remember, which is the only reason it survived. Robergs and Landwehr traced it to a 1971 chapter that plotted a hand-drawn line through a handful of studies, and it was never tested as a prediction equation. Its standard deviation runs 7 to 12 bpm, and it systematically underestimates max after about age 40. For a 60-year-old, 220 minus age says 160 while Tanaka says 166, a gap that shifts every zone downward and can leave older adults training easier than they should. That is why this calculator defaults to Tanaka and keeps 220 minus age only as a labeled option.

Worked examples (for quick reference)

Here are common scenarios so you can sanity-check the tool against your own profile. The last column shows how Zone 2 shifts when you add a resting heart rate of 60 bpm and switch to the Karvonen method.

Percent of max vs the Karvonen method

Both methods are legitimate. They just answer slightly different questions.

Percent of max is the quick method. You take your estimated max and multiply by the zone percentage. It needs only one input, your age, and it is what most watches use out of the box. The downside is that it ignores your resting heart rate, so two people with the same max but very different fitness get identical zones.

The Karvonen method, named for the 1957 work of Karvonen and colleagues, uses your heart rate reserve, the span between your resting and max heart rate. It scales each zone across that reserve and adds your resting heart rate back on top. Because a fitter person usually has a lower resting heart rate, their reserve is wider and their zones spread out to match. Karvonen zones tend to land a bit higher in bpm than percent-of-max zones at the same intensity, which is why the two columns in the calculator differ. If you know your resting heart rate, Karvonen is the more personalized choice. Measure it first thing in the morning before you get out of bed, ideally averaged over a few days.

Three things this calculator refuses to pretend

It cannot give you a precise number

No age formula can. Every equation here carries about a 10 beat per minute individual error. The calculator states that band plainly instead of hiding it behind a confident-looking single number. If your training genuinely depends on precision, the measured max override exists for exactly that reason.

220 minus age is not the standard

It is folklore that got embedded in firmware. The exercise physiology literature moved on decades ago. This tool defaults to Tanaka and treats 220 minus age as the legacy option it is.

One max does not fit both sexes equally

Most classic equations were built on mostly male samples. Gulati and colleagues found that female max heart rate falls slightly faster with age and sits lower overall, so a woman using a male-anchored formula can end up with zones that are too high. The Gulati option corrects for that.

How to find your real max heart rate

The formula is a placeholder. Two methods beat it for your individual number, and both are covered in our max heart rate research review.

Let your watch learn it. Garmin, Apple Watch, Whoop, Polar, and Coros all track your highest recorded heart rate and nudge your estimated max upward as your real ceiling appears. After a few hard sessions, check what max the watch has settled on and enter it in the measured field above.

Do a field test. After a thorough warmup, run or bike four to five minutes at the hardest pace you can hold, recover for two minutes, then finish with a 30-second all-out sprint. The highest number you see is a usable proxy for your true max. Only do this if you are healthy enough for near-maximal effort, and read the medical note below first.

When to ignore this calculator

These zones are built for healthy adults. A few situations call for professional input rather than a generic formula.

• Beta blockers and rate-limiting medications. These drugs lower your resting and maximum heart rate, so age formulas will overestimate your zones. Ask your prescribing clinician for zones from a supervised test, and train by perceived effort.
• Known cardiovascular disease or symptoms. Chest pain, unexplained shortness of breath, palpitations, or a history of cardiac events mean you should get cleared and get zones from a clinician-supervised stress test, not a web tool.
• Atrial fibrillation, pacemakers, or arrhythmias. Heart rate readings can be unreliable and the concept of a predictable max may not apply. Defer to your cardiology team.
• Pregnancy. Heart rate response to exercise changes across pregnancy. Follow the guidance of your obstetric care team rather than an age formula.
• Children and adolescents. Age-prediction equations were built on adults. They do not translate cleanly to growing bodies.

For everyone else, the calculator gives a defensible starting point. Use it, then refine with a field test or a watch-learned max as your fitness data accumulates.

Related reading

References

1. Tanaka H, Monahan KD, Seals DR. "Age-predicted maximal heart rate revisited." Journal of the American College of Cardiology. 2001;37(1):153-156. doi:10.1016/S0735-1097(00)01054-8
2. Gulati M, Shaw LJ, Thisted RA, Black HR, Bairey Merz CN, Arnsdorf MF. "Heart Rate Response to Exercise Stress Testing in Asymptomatic Women: The St. James Women Take Heart Project." Circulation. 2010;122(2):130-137. doi:10.1161/CIRCULATIONAHA.110.939249
3. Nes BM, Janszky I, Wisloff U, Stoylen A, Karlsen T. "Age-predicted maximal heart rate in healthy subjects: The HUNT Fitness Study." Scandinavian Journal of Medicine & Science in Sports. 2013;23(6):697-704. doi:10.1111/j.1600-0838.2012.01445.x
4. Robergs RA, Landwehr R. "The surprising history of the HRmax=220-age equation." Journal of Exercise Physiology Online. 2002;5(2):1-10. Open access PDF
5. Shookster D, Lindsey B, Cortes N, Martin JR. "Accuracy of Commonly Used Age-Predicted Maximal Heart Rate Equations." International Journal of Exercise Science. 2020;13(7):1242-1250. PMC7523886
6. Karvonen MJ, Kentala E, Mustala O. "The effects of training on heart rate; a longitudinal study." Annales Medicinae Experimentalis et Biologiae Fenniae. 1957;35(3):307-315. PMID:13470504

How this calculator differs from typical heart rate zone calculators

Most online heart rate calculators still default to 220 minus age, hand back a single max heart rate with no error band, and offer only the percent-of-max method. That combination quietly overstates precision. It gives one confident number built on a formula the research retired, then slices it without accounting for the individual variation that every study on the topic reports.

This calculator defaults to the Tanaka et al. 2001 equation, the most rigorously validated general-population formula, and offers Gulati for women and Nes for active adults so the math fits the person. It states the roughly plus or minus 10 bpm individual error out loud rather than hiding it, and it lets you override the whole thing with a measured or watch-learned max, which it openly recommends as more accurate than any equation. It builds zones two ways, percent of max and the Karvonen heart rate reserve method, so you can see how much your resting heart rate shifts the targets. And it puts the beta blocker warning where you cannot miss it, because for people on rate-limiting medication an age formula is not just imprecise, it is misleading. The trade is a less tidy single answer. The benefit is a number you can actually trust to train on.