What heart rate should I exercise at?

The rule: max heart rate and two target zones

The starting point is an estimated maximum heart rate, the fastest your heart is expected to beat during all-out effort. A common rough formula is 220 minus your age. This number is a benchmark, not a target you train at.

From that maximum, the American Heart Association describes two intensity zones. Moderate-intensity exercise sits at 50–70% of your maximum heart rate, and vigorous-intensity exercise sits at 70–85%. Moderate effort feels like a brisk walk where you can still talk but not sing; vigorous effort makes sustained conversation hard.

You can plug your own age into the Heart Rate Zones Calculator to see these numbers instead of doing the arithmetic by hand.

A worked example at age 40

Start with the formula: 220 − 40 = an estimated maximum heart rate of about 180 bpm.

Apply the two zones. Moderate intensity is 50–70% of 180, which works out to roughly 90–126 bpm. Vigorous intensity is 70–85% of 180, or roughly 126–153 bpm. So a 40-year-old aiming for a moderate session would expect a heart rate in the low-100s, while a harder push would climb toward 150.

The same math scales with age. Because the maximum estimate falls as age rises, an older person's zones sit at lower bpm values than a younger person's, even at the same relative intensity.

Why the estimate is rough, and what shifts it

The 220 − age formula is convenient but carries wide individual variation. Two people the same age can have genuinely different true maximums, so the estimate can be off by a meaningful margin in either direction. It describes a population average, not a specific individual.

A chest-strap or wrist heart-rate monitor gives a real-time reading of where you actually are, and a clinician-supervised stress test measures maximum heart rate far more precisely than any formula. Some medications also affect heart rate — beta blockers, for instance, can lower it — which means the formula-based zones may not line up with what a monitor shows.

Reading the zones as a standard, not a verdict

The percentages above are how the American Heart Association classifies exercise intensity, not a judgment about any one workout. A number outside these bands is not automatically "wrong"; it is simply information about how hard you were working relative to an estimated ceiling.

This is general information, not medical advice. Heart-rate targets, medication effects, and safe exercise intensity depend on individual health circumstances, so questions about your own numbers are best raised with a clinician who can account for your history and any prescriptions.