Why is it important to know your maximum heart rate? How long should you aim to stay in your target heart rate zone? Today, we’ll be answering these questions and more. Before we can get into all the good details, you’ll need to know your maximum heart rate.

How to Find Out Your Maximum Heart Rate

For a long time, the formula for calculating your maximum heart rate has been the same. 220 minus your age. Why should it change? Math is pretty straightforward isn’t it? Well, yes, it is, but biology isn’t.  

Experts have realized that this equation does not account for the fact that your heart rate naturally decreases with age. This means that your maximum heart rate also decreases with age.1

This study on the relationship between age and maximal heart rate offers a new, more accurate, formula that accounts for this finding: 

HR max = 207 – (0.7 x age) 

To give you a brief example, say your age is 39. You would perform the following calculation: 

HR max = 207 – (0.7 x 39) 

HR max = 207 – (27.3) 

HR max = 179.7 

You can easily round this number so it’s easier to remember. In this case, it would be 180. 

What Zone Should You Aim for During Cardio? 

Different heart rate zones can help define the amount of effort your heart is putting into pumping blood to your body. Your resting heart rate is the number of times your heart beats per minute when your body is at rest. A normal resting heart rate is typically between 60 and 100 beats per minute.2 

To benefit your heart, the American Heart Association recommends targeting at least 50% and up to 85% of your maximum heart rate.2  

50% to 70% is what we would typically consider moderate-intensity exercise.2 On many cardio machines, this is typically what’s labeled the “Fat Burn Zone.” While that sounds ideal, this zone actually burns fewer total calories and doesn’t give your heart as many benefits as the next level up. If you’re new to exercising, however, this zone might be just right. If your max HR was 180, the range you would be shooting for would look like this: 

180 x 0.50 = 90 

180 x 0.70 = 126 

With a max HR of 180, your heart rate would need to be between 90 and 126 for your heart to do moderate-intensity work. 

70% to 85% is considered high-intensity exercise.2 On cardio machines, this is typically labeled as the “Cardio Zone.” Most people will want to aim for this level of cardiovascular exercise to improve and maintain heart health and body weight. If your max HR was 180, the range you would aim for would look like this: 

180 x 0.70 = 126 

180 x 0.85 = 153 

Your heart rate would need to be between 126 and 153 for your heart to do high-intensity work. 

Anything greater than 85% of your maximum heart rate would be considered your Peak Heart Rate. In this zone, you’ll want to be careful of how much harder you push yourself, but aiming for this zone is typically how athletes train to improve performance and speed. 

How Long to Stay in Each Heart Rate Zone 

The guidelines established by the American College of Sports Medicine recommend that, if you’re new to exercise, you should stay in your target heart rate zone for only 10 minutes. As you increase your fitness and endurance, you should maintain it for anywhere between 45 minutes to an hour.3 

How To Track Your Heart Rate 

A lot of wearable trackers have heart rate monitoring capabilities, but our favorite is the MyZone Activity Belt. This heart monitor is worn around the chest. Not only is it more accurate than a wrist tracker (99.4% accurate!), you can go a month without recharging the battery, and the app can display your heart rate and calories-burned in real time! 

To learn more about how to care for your heart, read our article on How to Build a Strong Heart with Exercise. Or, read about why you should use fitness level, not just your weight, to evaluate your health. To access our monthly blog post highlights, subscribe to our newsletter today! 


  1. Gellish, Ronald L, et al. “Longitudinal Modeling of the Relationship between Age and Maximal Heart Rate.” Medicine and Science in Sports and Exercise, U.S. National Library of Medicine, May 2007, www.ncbi.nlm.nih.gov/pubmed/17468581. 
  2. “Know Your Target Heart Rates for Exercise, Losing Weight and Health.” Www.heart.org, American Heart Association, 2015, www.heart.org/en/healthy-living/fitness/fitness-basics/target-heart-rates. 
  3. Markowitz, Andrea. “Here’s How to Set Your Pace.” Chicagotribune.com, 13 May 2019, www.chicagotribune.com/lifestyles/ct-xpm-2011-01-26-sc-health-0126-heart-rate-monitors-20110126-story.html.