How do I track heart rate with my Fitbit device?

When your heart beats, your capillaries expand and contract based on blood volume changes. To determine your heart rate, the optical heart-rate sensor in your Fitbit device flashes its green LEDs many times per second and uses light-sensitive photodiodes to detect these volume changes in the capillaries above your wrist. Then your device calculates how many times your heart beats per minute (bpm).

We use green LEDS because they maximize the signal detected from the capillaries near the surface of the skin. The optical heart-rate sensor also uses infrared light to determine when the device is on your wrist to improve the accuracy of your heart-rate data.

Resting heart rate is the number of times your heart beats per minute when you’re still and well-rested. Typically, resting heart rate ranges from 60-100 bpm, but the rate can vary based on age and fitness level.

Why should I track resting heart rate in the Fitbit app?

Resting heart rate can be an important indicator of your fitness level and overall cardiovascular health. In general, active people often have a lower resting heart rate because their heart muscle is in better condition and doesn’t need to work as hard to maintain a steady beat.

How do I see resting heart rate data?

To see your current resting heart rate, swipe up from the clock face on your device. To see resting heart rate data for the past 30 days, tap the Heart Rate tile in the Fitbit app.

This data is also available in the Health Metrics tile:

1. In the morning, tap the Today tab Health Metrics .
2. See a graph of your resting heart rate.
3. For details, tap Learn More above the graph.

For more information, see What should I know about health metrics in the Fitbit app?

what factors can affect resting heart rate?

Several factors can affect resting heart rate: stress, alcohol or caffeine intake, or fever usually raise resting heart rate, while regular exercise or meditation can lower it. Air temperature and certain medications can also affect resting heart rate.

Heart-rate zones, which are percentages of your maximum heart rate, can help you determine the intensity of your workout or activity.

How does my Fitbit device calculate my heart-rate zones?

The formula Fitbit uses to calculate your heart-rate zones is based on your device.

Charge 4, Charge 5, Inspire 2, Ionic, Sense series, and Versa series

Fitbit personalizes your heart-rate zones using your heart rate reserve, which is the difference between your maximum heart rate* and your resting heart rate (source).

Heart rate reserve is an indication of your overall cardiovascular fitness. While your maximum heart rate is generally determined by age, your resting heart rate can be lowered by increasing your fitness level. By lowering your resting heart rate, you can increase your heart rate reserve.

For example, if you are 45 years old and your resting heart rate is 74 bpm, here’s the math:

First, calculate your maximum heart rate and heart rate reserve.

Metric	Calculation
Maximum Heart Rate	175 bpm Common formula of 220 - age (45)
Heart Rate Reserve	Maximum heart rate - resting heart rate
Target Heart Rate Per Zone	(Percentage of maximum heart rate × heart rate reserve) + resting heart rate

Next, use your heart rate reserve to calculate your personalized heart-rate zones.

Heart-Rate Zone	Calculation
Fat Burn Zone	114 to 134 bpm Bottom of zone: (0.4 × 101) + 74 = 114 bpm Top of zone: (0.59 × 101 ) + 74 = 134 bpm
Cardio Zone	135 to 159 bpm Bottom of zone: (0.6 × 101) + 74 = 135 bpm Top of zone: (0.84 × 101) + 74 = 159 bpm
Peak Zone	160+ bpm Bottom of zone: (.85 × 101) + 74 = 160 bpm Top of zone: maximum heart rate

Note that you can see your personalized heart-rate zones on the Active Zone Minutes screen in the Fitbit app.

*Occasionally during intense exercise, you might notice your heart rate go above your Fitbit-calculated maximum heart rate.

All other devices

Fitbit estimates your maximum heart rate* with the formula of 220 - your age, and calculates your heart-rate zones based on that number (source).

*Occasionally during intense exercise, you might notice your heart rate go above your Fitbit-calculated maximum heart rate.

What are the heart-rate zones on my Fitbit device?

Charge 4, Charge 5, Inspire 2, Ionic, Sense series, and Versa series

Personalized zones adjust as your fitness level or other factors change.

Icon	Zone	Description
	Below Zones Below 40% of your heart rate reserve	Below the fat burn zone, your heart beats at a slower pace. You’re at rest for now.
	Fat Burn Zone Between 40% and 59% of your heart rate reserve	In the fat burn zone, you’re likely in a moderate activity such as a brisk walk. Your heart rate and breathing might be elevated, but you can still carry on a conversation.
	Cardio Zone Between 60% and 84% of your heart rate reserve	In the cardio zone, you’re likely doing a vigorous activity such as running or spinning.
	Peak Zone Greater than 85% of your heart rate reserve	In the peak zone, you’re likely doing a short, intense activity that improves performance and speed such as sprinting or high-intensity interval training.

Custom Zones

Instead of using these 3 heart-rate zones, you can create a custom zone to target a specific heart rate:

1. From the Today tab in the Fitbit app, tap the Heart Rate tile .
2. Tap the Settings icon .
3. Tap Heart Rate Zones.
4. Tap the switch next to Custom Zone and enter your custom zone.

On fitbit.com, log into your dashboard, and click the gear icon in the top right. Click Settings Personal Info Heart Rate Zones and enter your custom zone.

All other devices

Icon	Zone	Description
	Below Zones Below 50% of your maximum heart rate	Below the fat burn zone, your heart beats at a slower pace. You’re at rest for now.
	Fat Burn Zone Between 50% and 69% of your maximum heart rate	In the fat burn zone, you’re likely in a moderate activity such as a brisk walk. Your heart rate and breathing might be elevated, but you can still carry on a conversation.
	Cardio Zone Between 70% and 84% of your maximum heart rate.	In the cardio zone, you’re likely doing a vigorous activity such as running or spinning.
	Peak Zone Greater than 85% of your maximum heart rate.	In the peak zone, you’re likely doing a short, intense activity that improves performance and speed such as sprinting or high-intensity interval training.

Custom Zones

Instead of using the 3 heart-rate zones, you can create a custom zone to target a specific heart rate:

1. Tap the Today tab and tap your profile picture Heart Rate Zones.
2. Enter your custom zone.

On fitbit.com, log into your dashboard and click the gear icon in the top right. Click Settings Personal Info and enter your custom zone.

Heart-rate variability (HRV) is the variation in time between heartbeats. If your heart rate is 60 bpm, your heart doesn’t necessarily beat once per second — a healthy heart isn’t like a metronome. Your autonomic nervous system determines the timing of each heartbeat.

HRV varies from person to person. Studies show that people with a higher HRV have better cardiovascular fitness and might be more resilient to stress. Mindfulness, meditation, sleep, and physical activity can help improve your HRV. A significant drop in HRV may indicate that your body is experiencing illness, stress, or depression or anxiety.

Note: This data is included in the Health Metrics tile in the Fitbit app. For more information, see What should I know about health metrics in the Fitbit app?

Why should I track heart-rate variability in the Fitbit app?

Track your HRV in the Fitbit app to help you gauge your overall well-being. Trends in HRV data can help you be more aware of how stress and lifestyle choices, such as nutrition and exercise, can affect your body

How does my fitbit device track heart-rate variability?

Fitbit uses the common formula called RMSSD to determine HRV from your recent heart-rate data. In the graph, your latest HRV measurement is from the longest sleep period over the past 24 hours. Only sleep periods greater than 3 hours are considered.

How do I see heart-rate variability in the fitbit app?

Wear your device for at least a full day, including to sleep at night. Then check your stats:

1. In the morning, open the Fitbit app and tap the Today tab Health Metrics.
2. See a graph of your nightly average heart-rate variability in milliseconds.
3. For details, tap Learn More above the graph.

what factors can affect heart-rate variability?

Several factors can affect HRV, including age, sex, sleep quality, stress, and lifestyle choices, such as nutrition and exercise.

Charge 5, Inspire 3, Sense, Sense 2, Versa 3, and Versa 4 notify you when we detect that your heart rate is outside of your high or low thresholds while you appear to be inactive for at least 10 minutes.

What happens when I receive a heart-rate notification?

When your Fitbit device detects your heart rate goes above or below your personal heart rate threshold while you’re inactive, you receive a notification on your device. Tap Open, and then tap the notification in the Fitbit app to learn more about your data and complete a survey where you log any potential factors, medications, and symptoms. You can use the information you log in the survey to track your heart health trends and share it with your healthcare provider.

How do I change my heart-rate notification thresholds?

To start, your thresholds are based on your age and typical resting heart rate. To adjust your thresholds:

1. From the Today tab in the Fitbit app on your phone, tap your profile picture your device tile.
2. Tap High & Low Heart Rate.
3. Turn on Custom in the High heart rate or Low heart rate section.
4. Tap Threshold and choose a new threshold.

To use your default thresholds, turn off the custom threshold.

How do I turn off heart-rate notifications?

1. From the Today tab in the Fitbit app on your phone, tap your profile picture your device tile.
2. Tap High & Low Heart Rate.
3. Turn off High heart rate notification or Low heart rate notification.

As with all heart-rate tracking technology, accuracy is affected by personal physiology, device location on your arm, and type of movement.

For a more accurate heart-rate reading:

• Wear your Fitbit device on top of your wrist, and make sure the back of the device is in contact with your skin.
• When you’re not exercising, wear your device a finger’s width above your wrist bone.
  

• During exercise, wear your device a bit tighter and higher for an improved fit. The band should be snug but not constricting (a tight band restricts blood flow, potentially affecting the heart-rate signal). 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.
  

Several factors can affect heart rate, including air temperature, stress level, alcohol or caffeine intake, immune response to illness, and medication use (source).

Exercising in cold weather can make it more difficult for your device to track your heart rate, as environmental conditions can affect skin perfusion (the amount of blood that flows through your skin).

Spikes in your heart rate during sleep may be caused by sudden movements (for example, waking up and getting out of bed), or a weak signal due to wrist placement.

Review our tips in How do I improve the accuracy of a heart-rate reading?

For any concerns about your heart-rate data, contact your physician.

At times, you might notice slight variations between your heart-rate reading on your Fitbit device versus on another device (such as a chest strap or another wrist-based heart-rate tracker) due to the differences in technologies.

Differences between heart-rate readings on your device and on exercise equipment are likely due to wrist or hand position. Make sure the back of your device is in contact with your wrist and that your band is snug.

Note that you might notice slight variations between your heart-rate reading on your new Fitbit devices compared with your old ones due to improvements in the heart rate sensor and algorithm.

To resolve common issues, see our troubleshooting steps in What factors can affect my heart-rate reading on my Fitbit device?

The LEDs on your device 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.

Note that the LEDs continue to flash if you turn off heart-rate tracking.