Track your heart rate continuously and automatically with your Fitbit device.
How does my Fitbit device detect my heart rate?
When your heart beats, your capillaries expand and contract based on blood volume changes. PurePulse LEDs (light-emitting diodes) on your Fitbit device reflect onto the skin to detect blood volume changes, and finely-tuned algorithms are applied to measure heart rate automatically and continuously. The heart-rate icon you see on the display tells you if you're in 1 of 3 heart-rate zones.
What are heart-rate zones?
Heart-rate zones can help you optimize your workout by targeting different training intensities. The default zones are calculated using your estimated maximum heart rate. Fitbit calculates your maximum heart rate with the common formula of 220 minus your age. The illustrations below provide examples for each zone. Note that the appearance of the icons may look slightly different between devices; for example, dots instead of dashes. For more information about zones, see the American Heart Association's Target Heart Rates article.
Peak zone, which means your heart rate is greater than 85% of maximum, is the high-intensity exercise zone. The peak zone is for short intense sessions that improve performance and speed.
Cardio zone, which means your heart rate is 70 to 84% of maximum, is the medium-to-high intensity exercise zone. In this zone, you're pushing yourself but not straining. For most people, this is the exercise zone to target.
Fat Burn zone
Fat burn zone, which means your heart rate is 50 to 69% of maximum, is the low-to-medium intensity exercise zone and may be a good place to start for those new to exercise. It’s called the fat burn zone because a higher percentage of calories are burned from fat, but the total calorie burn rate is lower.
Out of zone
When you’re out of zone, which means your heart rate is below 50% of maximum, your heart rate may still be elevated but not enough to be considered exercise.
Instead of using the 3 default zones you can create a custom zone if you're targeting a specific heart rate. From the Fitbit app dashboard, tap or click the Account icon (
and find Heart Rate Zones
. Then enter your custom zone.
On fitbit.com, log into your dashboard and click the gear icon in the upper right. Choose Settings
> Personal Info
. There you can enter your custom zone.
Note that on Fitbit Ionic and Fitbit Versa, the heart-rate value appears gray if your watch is searching for a stronger reading.
What is resting heart rate?
Resting heart rate measures your heart beats when you are still, and it can be an important indicator of the health of your heart. According to the American Heart Association website, “the average resting heart rate is 60-80 beats per minute, but it’s usually lower for physically fit people.” This is because “active people often have lower heart rates because their heart muscle is in better condition and doesn’t need to work as hard.” Also, the average resting heart rate rises with age. For more information, see the American Heart Association's All About Heart Rate article.
How is resting heart rate measured?
Resting heart rate refers to the heart rate measured when you’re awake, calm, comfortable, and have not recently exerted yourself. We use your heart rate data from when you’re awake and asleep to estimate your resting heart rate. For best accuracy, wear your device to sleep.
Your resting heart rate is usually higher than your heart rate while you are asleep, so don’t be surprised if your resting heart rate is higher than the lowest number that you see in your heart rate graphs.
What is max heart rate?
Max heart rate is used to calculate different heart-rate zones. Fitbit calculates your max heart rate with the common formula of 220 minus your age. Don't be concerned if occasionally during intense exercise your heart rate goes above your Fitbit-calculated max heart rate.
Instead of using the default, you can create a custom max heart rate if you're targeting a specific heart rate. In the Fitbit app dashboard tap or click Account
and find an option to change your heart-rate zones. From there you can create a custom max heart rate.
What factors can affect my heart rate?
Heart rate may be affected by any number of factors at a given moment. Movement, temperature, humidity, stress level, physical body position, caffeine intake, and medication use are just a few things that can affect your heart rate. Different medical conditions and medications can impact your heart rate. Consult your doctor before starting an exercise routine.
How do I improve the accuracy of my heart-rate reading?
As with all heart-rate tracking technology, accuracy is affected by personal physiology, location of wear, and type of movement.
When you’re not exercising, wear your device a finger’s width below your wrist bone. Fitbit’s PurePulse technology is designed to be most accurate when you wear your device on the top of your wrist.
For improved heart-rate accuracy, keep these tips in mind:
- Experiment with wearing the device higher on your wrist during exercise for an improved fit and more accurate heart-rate reading. Many exercises such as bike riding or weight lifting cause you to bend your wrist frequently, which could interfere with the heart-rate signal if the watch is lower on your wrist.
- Make sure the device is in contact with your skin.
- Do not wear your device too tight; a tight band restricts blood flow, potentially affecting the heart-rate signal. That being said, the device should also be slightly tighter (snug but not constricting) during exercise than during all-day wear.
- With high-intensity interval training, boxing, or other activities where your wrist is moving vigorously and non-rhythmically, the movement may prevent the sensor from finding an accurate heart rate. Similarly, with exercises such as weight lifting or rowing, your wrist muscles may flex in such a way that the band tightens and loosens during exercise. Try relaxing your wrist and staying still briefly (about 10 seconds), after which you should see an accurate heart-rate reading. Note that your device will still provide accurate calorie burn readings during these types of exercise by analyzing your heart rate trends over the course of the workout.
What is my cardio fitness score in the Fitbit app?
Cardio fitness score, Fitbit's estimate of your VO2 Max, is an indicator of overall fitness that can help predict performance for endurance-based activities including running, biking, and swimming (source
). For more information, see What is my cardio fitness score?
How do I turn off heart-rate tracking on my Fitbit device?
To preserve battery life on your device, you can turn off heart-rate tracking. Note that the LEDs on the back of your device will continue to flash.
Open the Settings
) > Heart Rate
Change your heart rate setting in the Fitbit app.
- From the Fitbit app dashboard, tap the Account icon ().
- Tap your device image.
- Tap Heart Rate, and then choose Off.
Are the LEDs on my Fitbit device safe?
Allergy to visible light is extremely rare, and the LEDs are on the visible spectrum, similar to the lights in your home or office. The LEDs have very low power so they won't burn your skin, and they're programmed to shut down if your device freezes or can't find a signal.
Why don't I see my heart rate on my Fitbit device?
Occasionally your device may have difficulty getting a strong signal. If you don't see your heart rate on your device, make sure you're wearing it correctly. Review the tips in How do I improve the accuracy of the heart-rate reading on my Fitbit device?
After a few moments, you should see your heart rate again. For additional troubleshooting steps, see Why don't I see my heart rate on my Fitbit device?