Target Heart Rate Calculator

Heart rate rises in step with how hard you are working, which makes it a convenient, real-time gauge of exercise intensity. A target heart rate is simply the range of beats per minute that corresponds to the intensity you are aiming for — usually moderate or vigorous aerobic activity.

This calculator uses the American College of Sports Medicine's definitions, which depend on the method. With the Karvonen method, moderate intensity is 40–59% of heart rate reserve and vigorous is 60–89%. With the percent-of-max method, moderate is 64–76% of maximum heart rate and vigorous is 77–95%.

You may also see simpler round figures: the American Heart Association's consumer guidance describes moderate exercise as about 50–70% and vigorous as about 70–85% of maximum heart rate. Both are reasonable guides; the ACSM figures are used here because they are defined for each method, so the two methods can be compared fairly.

The ranges are a guide, not a rule. A heart rate monitor or a 15-second pulse count multiplied by four tells you where you are, and you adjust pace until you sit in the band you want.

Maximum heart rate cannot be measured safely at home, so it is estimated from age. The best-known estimate is 220 minus age, but it was never validated in a sample with enough older adults. In 2001 Tanaka and colleagues analysed data from 18,712 people and arrived at 208 − 0.7 × age, which this calculator uses.

The two agree at 40 and diverge on either side. At 70 the traditional formula gives a maximum nine beats lower, which pulls every training target down with it and means an older exerciser following it may be working less hard than intended.

Either way, the result is an average for people of your age. Individuals vary around it — by around 10 bpm or more — and only a supervised maximal exercise test measures your true maximum.

The Karvonen method, from Karvonen and colleagues' 1957 study of the effects of training on heart rate, works on heart rate reserve: the difference between your maximum and your resting rate. You take a percentage of that reserve and add your resting rate back on.

Because it starts from your resting pulse, it gives a fitter person with a low resting rate a target matched to their own working range. The simpler percent-of-max method ignores resting heart rate entirely, and for the same percentage it gives lower numbers. That is why the two methods use different cut-offs: 60% of reserve and 60% of maximum are different efforts.

With matched cut-offs the two methods land close together for a typical resting heart rate. They part ways when resting heart rate is unusually low or high, which is where Karvonen's personalisation earns its keep.

To use Karvonen well you need a genuine resting heart rate: count your pulse for a full minute after waking, before you get out of bed, and average a few mornings.

Many fitness trackers divide the range from 50% to 100% into five zones of ten percentage points each. The zones and their names are a common training convention rather than part of the ACSM moderate and vigorous definitions. The result panel above lists them in beats per minute for your inputs and chosen method.

• Zone 1, 50–60%: very light — warm-ups, cool-downs and recovery.
• Zone 2, 60–70%: light — comfortable, conversational endurance work.
• Zone 3, 70–80%: aerobic — sustained steady efforts.
• Zone 4, 80–90%: threshold — hard work you can hold for limited periods.
• Zone 5, 90–100%: maximum — short intervals only.

Zone boundaries are a convention rather than physiology, and different brands draw them differently. The so-called fat-burning zone is the lower zones relabelled: the share of energy from fat is higher at low intensity, but total calories burned per minute are lower.

Several common situations make heart rate a poor guide to effort:

• Beta-blockers and some other heart and blood pressure medicines lower heart rate and blunt its rise during exercise, so age-based targets will be unreachable or misleading.
• Pregnancy changes resting and exercise heart rate; follow the advice of your maternity care team.
• Heart conditions, including rhythm disorders such as atrial fibrillation, mean targets should come from your cardiologist or a supervised exercise test.
• Heat, dehydration, caffeine, illness and poor sleep all raise heart rate for the same effort.
• Wrist-worn optical sensors can lag or misread during intervals and strength work.

The CDC describes two simple alternatives that work regardless of medication or device:

• The talk test: during moderate activity you can talk but not sing; during vigorous activity you can say only a few words before pausing for breath.
• Perceived exertion: on a 0–10 scale where sitting is 0 and all-out effort is 10, moderate activity is about 5 or 6 and vigorous activity starts at about 7 or 8.

Many people find it useful to calibrate the two: note your heart rate when the talk test says moderate, and use that as a personal check on the calculated range.