How does Garmin measure sleep?

In this guide, we will talk about how Garmin measures sleep, what is Advance Sleep Monitoring, some of the compatible devices and additional considerations when using Garmin for sleep tracking purposes. 

How does Garmin measure sleep?

If you wonder how Garmin measures sleep, here we have the answer. Garmin measures sleep just the same way other devices such as watches, wristbands, smartphones and bed strips do since they have movement sensors (i.e. accelerometer). The method they use is called actigraphy and the baseline is that if you move just a little, you are in deep sleep, if you move a lot then you are in light sleep, and so on.

Additionally, another method of measuring sleep is called polysomnography but it is mainly found in EEG equipment. 

We know for a fact that the quality of our sleep influences the rest of our day. Let’s think about it for a minute. If you have been partying the night before and just slept 3 hours because you had to get up really early in the morning to go to sleep, How would you feel? I know I will be very irritable, moody and very tired. Moreover, many users get a Garmin device not only to track their activities but also because they are interested in measuring their sleep.

Tracking your sleep may help you set new habits and improve the quality of your sleep. Moreover, if you track your sleep and you can see you ha

Advanced Sleep Monitoring

New Garmin watches have a feature called Advanced Sleep Monitoring or ASM. With ASM, users can have the ability to track their sleep in Garmin Connect when they are wearing the device at night when they are sleeping. ASM is available mainly on watches that have an optical heart rate sensor. 

Some of the devices compatible with advance sleep monitoring are:

  • Approach S62
  • D2 Charlie
  • D2 Delta series
  • Descent Mk1
  • Descent Mk2 series
  • fenix 5 series
  • fenix 5 Plus series
  • fenix 6 series
  • Forerunner 245 series
  • Forerunner 45
  • Forerunner 45S
  • Forerunner 645 series
  • Forerunner 745
  • Forerunner 935
  • Forerunner 945
  • Garmin Swim 2
  • Instinct series
  • Legacy Hero Series – Captain Marvel
  • Legacy Hero Series – First Avenger
  • Legacy Saga Series – Darth Vader
  • Legacy Saga Series – Rey
  • MARQ Collection
  • quatix 5 series
  • quatix 6
  • tactix Charlie
  • tactix Delta
  • Venu
  • Venu Sq series
  • vivoactive 3 series
  • vivoactive 4 / 4S
  • vivomove HR
  • vivomove 3
  • vivomove 3S
  • vivomove Style
  • vivomove Luxe

 Is Garmin accurate when measuring sleep?

As indicated by Garmin Support, to get the most accurate sleep data:

  • Wear the device at least 2 hours before bedtime and keep it on while you are sleeping.
  • Make sure the device’s heart rate monitor is on, and the device fits you comfortably, not too tight or loose.
  • If you own more than one activity tracker, set the device with an advanced sleep monitor as your ‘Preferred Activity Tracker’. 
  • Under the Garmin Connect User setting, make sure there is a valid birth date. 
  • Make sure that your average sleep and wake times are set correctly. 

What information is recorded with ASM?

The information recorded with ASM are sleep cycles. Garmin is introducing sleep cycles that will provide information related to light sleep, deep sleep and REM sleep. 

During light sleep, eye movements and muscle activity begin to slow down as your body is preparing to go into a deep sleep. During this next stage, deep sleep, eye and muscle movements will stop completely and your heart rate and breathing pattern slow down. This stage is also referred to as restoration mode, where the body recovers, builds bone and muscle and boosts your immune system.

During the Rapid Eye Movement stage or REM is where you dream and brain activity is almost as active as when you are awake. REM is very important to form and consolidate memories and learning.

However, considering that Garmin Advance Sleep doesn’t track naps, for me it is a great inconvenience because I do like to nap from time to time. In fact, there is a lot of research available showing the benefits of napping but the app will only take into consideration the length of sleep.  

Additionally, we have the Pulse Oximetry or Pulse Ox for short. This is a non-invasive method used to measure the saturation of oxygen in your bloodstream. Finally, AMS also measures respiration, which is a feature that will display how many breaths you take a minute. 

Heart Rate Variability (HRV)

The optical heart rate sensor on the device will measure Heart Rate Variability which is the time measured between each heartbeat. Combined with the accelerometer, it allows Garmin to determine when you have fallen asleep when you’re awake and the sleep cycle you are in.

Some of the requirements to get ASM to include having a watch that is compatible with AMS, having the Garmin Connect App updated, the device must be worn at least 2 hours before going to bed and make sure the optical heart rate monitor is enabled. 

As indicated on, “Your ‘sleep clock’ is triggered to start when you get into bed and your heart rate drops to the levels the watch knows you sleep at. Based on your HRV this becomes more accurate the longer you wear the watch”. Unlike measuring your normal heart rate, which is the average number of heartbeats per minute, HRV focuses on small fluctuations of your heart. 

However, those fluctuations can be affected by many things such as age, body position, body weight, time of the day, stress, etc.

What Garmin Sleep reveals

After a good night’s sleep or in some cases a short (and not so good) night’s sleep, you can see the breakdown of the time you have spent in the different sleep stages and also the duration of any periods when you were awake.  However, the sleep stats will not be displayed on the watch itself but the Garmin Connect app or web tools.

Moreover, the app allows you to add a widget to get your most recent sleep time displayed on your ‘My Day’ screen. Also, you can get the breakdown by hitting ‘More’ and then tap into your health stats. If you see the timeline presented and you spot an error, you can manually edit the information in the Garmin Connect app and the web tools. 

But what about Pulse Ox? Well, since this measure will be recorded as you are sleeping, you will see a movement line showing the level of oxygen in your blood, also known as SpO2. The normal range is between 94 to 100% range. If you get a score particularly below 90% it may be a sign of health issues (i.e. sleep apnea). 

Why is this blog about How does Garmin measure sleep important?

As we have discussed on how Garmin measures sleep, it is pretty similar to other devices. However, this doesn’t mean it makes sleep tracking less interesting. In fact, we find fascinating how this kind of technology is able to record sleep cycle stages with such accuracy. The only thing we would have to say is a feature left to be improved is that Garmin won’t take naps into consideration when recording the data. 

Please feel free to leave any comments or thoughts about the content of this article!

Frequently Asked Questions (FAQs) about How does Garmin measure sleep

How does Garmin know when you’re sleeping?

Garmin knows when you are sleeping through the heart rate sensor on the device, estimating your heart rate variability, which combined with the accelerometer, will allow the device to estimate when you fall asleep when you wake up and in what level of sleep you are currently in. 

How does Garmin measure REM sleep?

In addition to the accelerometer data that Garmin has been using for sleep tracking, it is using heart rate variability data from the optical HR sensor to provide REM sleep tracking with this update. Make sure your device’s heart rate monitor is on, and the device fits snugly but comfortably.

Is Garmin sleep tracking accurate?

According to Garmin, “The work provides evidence that a wearable device using only actigraphy and optical heart rate sensors can estimate sleep stages of users to nearly 70% accuracy with a good Cohen’s kappa of 0.54 +/- . 12”. 

Why is my Garmin not tracking my sleep?

If your Garmin is not tracking your sleep, make sure you are wearing the device while you sleep and it is not too loose or tight. Also, note that statistics such as sleep levels and movement will not be recorded if you are not wearing the device when sleeping. The sleep monitor may stop if the device detects movement that indicates you are awake for an extended period during the night.

Is Garmin or fitbit better?

Determining which one is better, if Garmin or Fitbit, we have to consider what each device offers and the needs of the user. For instance, Garmin offers a greater emphasis on VO2 max and heart rate zones, making it the top choice for athletes. However, Fitbit is preferred by users who wish to have a lifestyle tracker. 


What is Advanced Sleep Monitoring in Garmin Connect?