Home » Fitbit

How Does Fitbit Track Sleep? (What You Need to Know)


The ability to track sleep is one of Fitbit’s strongest features. And, in my opinion, the brand has tried to make the technology as useful as possible. But how does Fitbit track sleep in the first place?

Fitbit devices track sleep using a combination of your heart rate’s reading, stillness that lasts about an hour, and small movements like rolling in your sleep. Heart rate and movement data makes it easy for Fitbit to give a more accurate analysis of your sleep cycle. 

Built to be as precise as possible for sleep tracking, Fitbit models such as Versa 2, Sense, Charge 4, and Charge 5 can show you your sleep stages and tell you how long you’ve been asleep.

And the goal is simple.

Fitbit want you to understand your sleep patterns and quality, so you can develop better sleeping habits and get the best sleep possible. 

4 Best Fitbit for Sleep Tracking

The best Fitbit for sleep tracking is the one that gives you the data you can depend on. It might not be 100% accurate, but the results should be useful enough to help you improve the quality of your sleep.

If you’re currently looking for a sleep tracker, and you’ve opted to settle for a Fitbit as your first choice, below are four options that I strongly recommend:

These Fitbits do a good job when it comes to sleep tracking.

In addition to giving you helpful data, Charge 4, Versa 2, Luxe, and Charge 5 also include Fitbit sleep scores, which can go a long way to help you improve the quality of your slumber.

How Does Fitbit Know You’re Asleep?

Fitbit knows you’re sleeping by measuring your brain activity, heart rate, and muscle movements. Then, it uses the resulting measurements to make an approximation of your sleep status.   

With the help of advanced signal processing and machine learning set of rules, a Fitbit can measure heart rate variability in your sleep, making it easy to determine whether your body is in movement between different levels of sleep.  

I should mention that not all Fitbit models have the ability to track sleep stats.

The recommendation list I’ve shared above are the ideal options to consider, particularly because they’re current, with the sleep-tracking technology being near accurate as possible.

Another important rule to keep in mind is you have to wear the Fitbit for an entire night for the sleep-tracking technology to work. 

Fitbit determines how much time you spend sleeping by subtracting awake and restless time from your overall sleep time.

Fitbit Sleep Stages Explained

There are four Fitbit sleep stages in total. And it’s important to learn about all of them to know exactly what they mean.

These stages are: 

  • Awake
  • Light sleep
  • Deep sleep
  • REM sleep

To be abundantly clear, Fitbit sleep stages depend on accelerometer data, a set of rules, and heart rate variability to determine how much time you spend in each stage. 

Here’s an explanation of each stage:

1. Awake

Awake is a sleep stage that indicates how many times you’ve woken up during sleep, with the normal range being between 10 to 30 times every night.

I’m someone who tosses and rolls over every time during the night, not to mention use the bathroom at least twice during a full sleep cycle. And I can confirm that the awake sleep stage doesn’t give scary data at all.

2. Light Sleep

The light sleep stage is where your body slows down and gets into the level where you start to fall asleep. But you can as easily wake up, causing the sleep tracking to jump back to the awake moment.

From what I understand, light sleep is the stage where, despite being asleep, you’re fully aware of everything going on around you.

In this stage, even a gentle touch from a person will be enough to wake you up.

Your heart rate will decrease in light sleep. At the same time, you’ll experience mental and physical recovery and feel better about yourself.

3. Deep Sleep

Deep sleep is where your body relaxes completely from the long day you’ve had. In this stage, your body is completely unresponsive, your muscles are more relaxed, and your breathing tends to be slower than when awake.

Your heart rate switches from decreasing to regular. And in addition to boosting your immune system and helping with physical recovery, deep sleep can help with memory improvement.

4. REM Sleep

REM stands for Rapid Eye Movement.

In this Fitbit sleep stage, your eyes shift from side to side, your brain become active, and your heart rate increases. It’s in this stage that you might dream, but your muscles tend to remain inactive to keep you from acting out what you see in those dreams.

REM takes place in the second half of the night and it usually lasts longer than the other three stages that I’ve discussed in this guide.

How Accurate is Fitbit Sleep?

Our expectation with smartwatches and fitness trackers is often quite simple:

Every one of us is interested in investing in a wearable technology that guarantees the best results possible. And we tend to look for 100% precision.

The accuracy of Fitbit sleep is no doubt something we need to consider when discussing how Fitbit tracks sleep.

To be very clear, your Fitbit can give you an estimation of your sleep.

Using heart rate variability and body movement, which varies from time to time based on physical and psychological factors, you should expect your Fitbit to give you varying sleep data from night to night.

As to whether Fitbit sleep technology is accurate, research shows that it’s unlikely you’ll get a 100% accuracy level.

Expect a 69% accuracy from the latest Fitbit devices, with the possibility of getting useful data from the Fitbit app if you continue to use the sleep-tracking feature more often.

How to Check Fitbit Sleep Stats

You can access your Fitbit sleep data in the Fitbit app.

  • Start the app and sync your Fitbit.  
  • Scroll all the way down on your profile and tap on “Today”.
  • Tap sleep entry, which will direct you to a page where you see detailed sleep data.
  • Swiping the graph will show you the duration of your sleep, your sleep routine, and sleep stages.
  • Look below the graph to find your sleep cycles, which shows more details about your stages all night long.

You can choose the day you want to view and compare your data accordingly. The data can be quite useful in helping you develop a healthier sleeping habit.

Note that the app shows your results on what the brand refers to as the sleep tile.

Related Reading

Frequently Asked Questions

1. What Does a Normal Sleep Pattern Look Like on Fitbit? 

A normal sleep pattern on Fitbit is one that shows you’re getting a good night’s sleep, which is what you should be aiming for. It’s normal to wake up or feel restless at the end of every sleep stage, but that shouldn’t occur regularly if you have good sleeping habits in place.

2. What is Restless Sleep on Fitbit? 

Restless sleep on Fitbit means you tossed and turned in your deep sleep excessively. In this case, your smartwatch or activity tracker will record this data as time spent awake.

It’s normal to have restless sleep, with 10 to 30 rounds of turns and tosses being fine. Still, you should aim to get at least 7 to 8 hours of sleep for adults.

3. How Does Fitbit Know You’re in REM Sleep?

Fitbit monitors changes in your heart rate to determine whether you’re in REM sleep or a completely different stage.

An increase in heart rate indicates that your body has entered the REM sleep, and your brain tends to be more active during this period.

4. How Does Fitbit Track Sleep When Not Wearing?

Fitbit can’t track sleep without wearing.

Remember, all Fitbit models are wrist based, and you must have one snug on your wrist while sleeping to track movements and heart rate for the device to be able to monitor your sleep and give you an accurate estimate of your sleep score on the Fitbit app.

You should not wear your Fitbit in a clip or as a pendant because doing so can’t get you any result when it comes to sleep tracking.  


Fitbit is inarguably a leader in the smartwatch and fitness tracker brand in the market. And the company has worked so hard to make sure every model in their product series deliver the best results possible.

When it comes to tracking sleep, the brand equips its models with the right technology to get the job done.

Keep in mind that you need to have slept for at least three hours for Fitbit to start recording your sleep stages.

The tracker shouldn’t be too loose or too tight on your wrist. Also, I strongly suggest that you charge the device at least three hours before you go to sleep, as the sleep-tracking feature doesn’t work on low battery.  

Photo of author

Michael Jonathan

Michael Jonathan is the brainchild of Apelo Studio. He loves talking about wearable devices, and he is passionate about helping you push your wearable device to its limits. His creativity and ability to tear electric components apart and put them back together makes him an incredible troubleshooter and blogger.

Leave a Comment