Calculadora de Frequência Cardíaca Alvo

Target heart rate zones are used to gauge how hard the cardiovascular system is working during exercise, based on the idea that heart rate rises in a fairly predictable way as exercise intensity increases. This calculator can estimate target zones using the simple percentage-of-maximum method or the Karvonen heart-rate-reserve method, which also factors in resting heart rate for a more individualised estimate.

A fórmula

Estimated max HR (traditional) = 220 - age. Estimated max HR (Tanaka) = 208 - 0.7 x age. Karvonen target HR = ((max HR - resting HR) x intensity %) + resting HR

• age = age in years
• resting HR = resting heart rate in beats per minute, ideally measured after several minutes sitting quietly
• max HR = estimated maximum heart rate in beats per minute
• intensity % = the target training intensity, expressed as a decimal (for example 70% = 0.70)
• heart rate reserve = max HR minus resting HR, the range the Karvonen method scales by intensity

"220 minus age": origin widely attributed to Fox, Naughton and Haskell, 1971 (a rough clinical rule of thumb, not derived from a dedicated study). Tanaka, Monahan and Seals, "Age-Predicted Maximal Heart Rate Revisited", Journal of the American College of Cardiology, 2001. Karvonen method: Karvonen, Kentala and Mustala, 1957.

How the calculation works

The simplest approach estimates maximum heart rate from age alone and then takes a percentage of that number as the target zone. The "220 minus age" formula has been used this way for decades because it is easy to calculate, but it was never derived from a rigorous, representative study; it is more of a widely adopted clinical approximation that happens to have stuck.

The Karvonen, or heart-rate-reserve, method refines this by also accounting for resting heart rate. It calculates the gap between estimated maximum heart rate and resting heart rate (the heart rate reserve), then scales that gap by the desired intensity percentage and adds resting heart rate back in. Because it incorporates a person's actual resting heart rate rather than relying on age alone, Karvonen-based targets are generally considered more individualised than a flat percentage of estimated maximum heart rate, particularly for people whose resting heart rate is notably higher or lower than average due to fitness level or other factors.

Whichever method is used, the result is still built on an estimated maximum heart rate, not a measured one, so the final target zone carries the combined uncertainty of that estimate plus the chosen formula.

How to read your result

Target zones are usually expressed as a percentage range of either estimated maximum heart rate or heart rate reserve. The table below summarises the American College of Sports Medicine intensity classifications commonly used to interpret these zones for aerobic exercise.

Why the 220 minus age formula is being replaced

The "220 minus age" rule has been in wide circulation since the early 1970s, but it was never based on a large, carefully controlled dataset; it originated as a summary approximation and was later shown to systematically overestimate maximum heart rate in younger adults and underestimate it in older adults. Individual variation around the formula is also substantial, with actual maximum heart rate for people of the same age commonly differing by 10 to 20 beats per minute or more from the formula's prediction.

The Tanaka equation, 208 minus 0.7 times age, was developed from a meta-analysis pooling data across a large number of studies and a wide age range, and is generally regarded as a more accurate population-level estimate, particularly for older adults, where the traditional formula tends to understate true maximum heart rate the most. Neither equation eliminates individual variability; both remain population averages rather than a measurement specific to any one person.

For anyone who wants a more precise number, a supervised graded exercise test with direct heart rate monitoring is the only way to measure, rather than estimate, true maximum heart rate. Age-based formulas remain useful for general guidance and rough zone-setting when a direct test is not practical or necessary.

Limitações

• Both the traditional and Tanaka formulas are population averages; an individual's true maximum heart rate can differ from either estimate by a wide margin, especially in older adults, highly trained athletes, and people with certain heart conditions.
• Heart rate can be affected by medications (particularly beta-blockers and some other cardiovascular or psychiatric medications), caffeine, dehydration, illness, heat, altitude and stress, none of which this calculator accounts for.
• The Karvonen method is only as accurate as the resting heart rate entered; a value measured after activity, caffeine, or while stressed will distort the resulting target zone.
• These formulas are general population estimates and are not validated for children, pregnant individuals, or people with diagnosed cardiovascular, pulmonary or metabolic disease, who may need a clinician-supervised exercise prescription instead.
• A target heart rate zone is a general training guide, not a medical safety threshold; reaching or exceeding an estimated zone is not, by itself, a sign of danger, and staying within a zone does not guarantee an exercise session is safe for a given individual.
• This tool does not replace an exercise stress test or clinical assessment for anyone with existing heart disease, chest pain, unexplained shortness of breath, or other cardiac symptoms.

Perguntas frequentes

Why does 220 minus age still get used if it is less accurate?

It is simple to calculate, widely known, and "close enough" for general fitness guidance in many younger and middle-aged adults. The Tanaka formula (208 minus 0.7 times age) is generally regarded as more accurate across a broader age range, particularly for older adults, but the older formula remains common in gyms, fitness equipment and general references out of habit.

What is the difference between the Karvonen method and a simple percentage of max heart rate?

A simple percentage of max heart rate only considers age. The Karvonen method also factors in resting heart rate, calculating a target based on someone's heart rate reserve rather than their estimated maximum alone. This generally produces a more individualised target, particularly for people with a resting heart rate well above or below the typical average.

What resting heart rate should I use for the Karvonen method?

Ideally, a heart rate measured first thing in the morning before getting out of bed, or after sitting quietly for several minutes, averaged over a few days for consistency. A resting heart rate taken shortly after activity, caffeine, or stress will not reflect a true resting value and will skew the calculated target zone.

Is it dangerous to exceed my target heart rate zone?

Briefly exceeding an estimated target zone is not automatically dangerous for most healthy people, since the zone is a training guide rather than a medical limit. Anyone with a diagnosed heart condition, chest pain, unusual shortness of breath, dizziness, or other concerning symptoms during exercise should stop and seek medical evaluation rather than relying on a heart rate number.

Do medications affect target heart rate calculations?

Yes. Beta-blockers and some other heart or blood pressure medications lower both resting and exercise heart rate, which makes age-based formulas and standard target zones less reliable. Anyone taking heart-rate-affecting medication who wants an accurate individual training zone should ask their prescribing clinician or a supervised exercise program for guidance.

Referências

1. American Heart Association. Target Heart Rates Chart.
2. National Heart, Lung, and Blood Institute (NIH). Heart-Healthy Living: Physical Activity.
3. Centers for Disease Control and Prevention. Physical Activity Basics.
4. American College of Sports Medicine. ACSM home.