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by Women's Health Updated 08/21

A heart rate monitor is an excellent tool for monitoring exercise intensity—but it won’t do you any good if you don’t know your maximum heart rate. Most people use the standard formula to calculate maximum heart rate—220 minus your age—but it turns out, that formula is usually wrong.

That’s right—that formula that you thought was carved in stone may be wrong. And as a result, you might not be exercising as intensely as you need to be.

Researchers used data from the HUNT Fitness Study to examine the relationship between age and maximum heart rate. The study included 3,320 healthy Norwegian adults who participated in a maximal exercise test—where they reached their maximum effort and heart rate. Researchers used linear modeling to determine the effect of age on the maximum heart rate reached. The results were astounding.

Overall, the standard maximum heart rate formula underestimated maximum heart rate in 77 percent of participants. In fact, the standard formula produced too-low results for up to 90 percent of participants between the ages of 40 and 60. What’s more, in participants between the ages of 60 and 69, the formula under-predicted maximum heart rate by as much as 15 beats per minute.

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Why does this matter? Knowing your true maximum heart rate is crucial for reaching optimal intensity during exercise. If you want to increase fitness and lose weight, you should spend the majority of your exercise time between 70 and 85 percent of your maximum heart rate. However, if you have underestimated your maximum heart rate, you’re not working as hard as you think you are—and you’re not going to see results.

Until now, the formula has been a convenient, easy way to predict maximum heart rate—but the researchers from this study caution that people who use the formula need to accept a standard error of 10.8 beats per minute.

So, how do you find your maximum heart rate if the formula is unreliable? There are several other ways:

  • Professional VO2Max Testing: VO2 Max is the maximum rate of oxygen consumption as measured during incremental exercise. Many professional athletes use this clinical test. The test involves progressively increasing intensity on a treadmill or stationary bicycle while wearing equipment that measures ventilation and oxygen and carbon dioxide concentration of the inhaled and exhaled air. This type of testing can be expensive and is usually reserved for professional athletes.
  • Race Test: Enter a 5K race. Wear your heart rate monitor. During the last few minutes of the race, go as hard as you can. Check your heart rate after the race and add 5 beats to the highest number recorded during your final sprint. This is an estimate of your maximum heart rate.
  • Four-Minute Test: Strap on a heart rate monitor and warm up for about 15 minutes. Perform a four-minute interval at the highest heart rate you can sustain for the entire four-minute period. Recover for two minutes and then repeat. Take the average of the two four-minute intervals to estimate your maximum heart rate.


  1. Nes BM, Janszky I, Wisløff U, et al. Age-predicted maximal heart rate in healthy subjects: The HUNT Fitness Study. Scandinavian Journal of Medicine and Science in Sports. 2013; 23(6): 697-704.