What Is Your MHR — and How Do You Calculate It?

A good high-intensity interval training (HIIT) workout can really get your heart racing — but tracking your heart rate can help you make sure you're getting the most out of your exercise routine.

In order to gauge your target heart rate to make sure you're logging a solid workout, you first need to know your maximum heart rate or MHR, which is the fastest rate at which your heart can safely beat each minute during exercise.

While getting a precise measure of your MHR probably requires a trip to the doctor, you can perform a quick calculation to get a good estimate at home (or at the gym). From there, you can use this value to guide your workout intensity.

Advanced heart rate monitors at a doctor's office are the most accurate way to measure MHR. But there are three calculations — called the Fox, Tanaka and Gulati formulas — that are all valid methods to estimate your max heart rate on your own, Matt Cheng, CSCS, tells LIVESTRONG.com.

The Fox formula is the most commonly referenced formula for calculating your MHR, and it's used by many major health organizations, like the Centers for Disease Control and Prevention (CDC) and the Mayo Clinic.

The Fox method, says cardiologist Steve Atchley, MD, is often recommended for its simplicity, while the Tanaka formula "is the more accurate of the two," he says (more on that below).

To find your MHR with the Fox method, all you need to do is subtract your age from 220.

The Fox formula: 220 - your age

The Fox formula, which has been around for decades, has been criticized for neglecting to incorporate research surrounding MHR in older adults. The Tanaka formula was developed in response to that in 2001, after analyzing MHR values from 351 different studies with more than 18,000 subjects of different ages and sexes. The Tanaka formula, first published in January 2001 in the Journal of the American College of Cardiology, better factors in age-related changes in MHR.

To calculate your max heart rate with the Tanaka method, multiply your age by 0.67, then subtract that value from 206.9.

The Tanaka formula: 206.9 - (0.67 x your age)

However, neither the Fox nor the Tanaka method adequately takes a person's sex into consideration (and a person's sex can affect max heart rate and exercise capacity). MHR formulas have traditionally been calculated based on data from men, so in a June 2010 study published in Circulation, researchers developed the Gulati formula.

The Fox and Tanaka methods overestimate maximum heart rate for women, according to the research, which might make women exercise harder than necessary if they're training within target heart rate zones, leaving them excessively fatigued or burned out.

The Gulati formula can more accurately predict max heart rate in women. Multiply your age by 0.88, then subtract that value from 206.

The Gulati formula: 206 - (0.88 x your age)

After you calculate your MHR, you can use that number to find out how hard you're working based on your age. Exercising within a target heart rate zone can help strengthen your cardiovascular system and build lung capacity, according to the Mayo Clinic.

• For a moderate workout, exercise within 50 to 70 percent of your MHR.
• For a more intense workout, exercise within 70 to 85 percent of your MHR.

You can also pick a heart rate goal based on your activity. For HIIT workouts, for example, you'll want to reach about 80 to 95 percent of your maximum heart rate during your most intense intervals, Cheng says. On the other hand, the ideal heart rate for low-intensity steady-state cardio like jogging or cycling is between 60 and 80 percent of your MHR.

Depending on your fitness level, you can decide which end of the heart rate spectrum you want to hit during your workouts. If you exercise often, you can train toward the higher end of the range, but if that feels unsustainable, ease off the intensity. To be safe, keep your hardest intervals to under a minute.

Always make sure you're incorporating rest and active recovery in your exercise plan. You shouldn't hit your MHR in every single workout.

And while you can exceed your maximum heart rate, it's not something that can typically be done through exercise, Dr. Atchley says. Usually, an excessive heart rate (called tachycardia) occurs only with abnormal heart conditions, the use of certain medications or elevated thyroid hormones.

Most activity trackers are built with a heart rate monitor that can estimate your beats per minute during your workout. Although the precision of many fitness tracker measurements is still up for debate, most devices are within 5 percent accuracy for heart rate, according to a May 2017 study in the Journal of Personalized Medicine.

Or, you can always measure your heart rate the old fashioned way: by checking your pulse. While you're exercising, stop briefly and take your pulse for about 15 seconds, according to the Mayo Clinic. Place your index and middle fingers on your neck or on the inside of your wrist. Count the beats for 15 seconds, and then multiply that number by four to get your beats per minute.

Checking in on your rate of perceived exertion is another way to gauge your effort without actually measuring your heart rate. Perceived exertion is how hard you feel that your body is working on a scale of six to 20, six being no exertion at all and 20 being max effort, according to the CDC. This method is subjective, but it can still be a convenient, quick measure of how hard you're working.

Understanding your MHR can help you make sure you're exercising at the proper intensity for your goals. Heart rate-based exercise personalizes your training to take it to the next level, so if it's a possibility for you, consider investing in a wearable heart rate monitor, Cheng says, or try a workout class like Orangetheory Fitness, where every participant wears a heart rate monitor.

Just don't let your heart rate become the sole focus of your workout. "If you find yourself taking extra lengths of time to calculate formulas, distracting you from your workout, it's best to practice on rest days or hire a professional to monitor your heart rate for you," Cheng says.