Garmin Sleep Coach – An Explainer

Garmin Fenix 7 rem deep Sleep stage
Fenix 7

Garmin Sleep Coach – Complete BS – Insights & An Explainer *OPINION*

Skip through to the end if you want to know why I think this is all complete BS. For starters, here’s an explainer on how Garmin Sleep Coach officially ‘works’.

Garmin’s Sleep Ecosystem

On paper, the recently expanded Garmin Sleep ecosystem looks pretty good. We have advanced sleep tracking that, among other things, breaks down the full duration of your night’s sleep into the various sleep stages. Also added to that is a simple numeric score out of 100 and a corresponding one-word summary like ‘Good’. Plus, some watches also have a sentence or so giving a slightly more detailed, written summary.

The same data is on Garmin Connect, except here you can also see trends and overlay other data like Resting HR, and add some notes. There’s nothing here that’s especially unusual compared to the competition. It’s nice though, don’t get me wrong. All the bases are covered.

Well, at least the bases are now covered as Garmin’s Venu 3 becomes the company’s first wearable to add NAP detection and SLEEP COACH, the latter of which is the subject of this article.

Two more features worth mentioning are the watch-based ‘reports’ that wrap around your sleep. So, a few hours before your usual bedtime, you should receive the Daily Summary (Evening Report), and in the morning, you get the appropriately named Morning Report. The evening report is new and disappointing, only providing a very simplistic yet seemingly correct summary of the kind of day you’ve had. On the other hand, the Morning Report is excellent; it’s truly personalized and has great options for configuring just the bits of info you want to see. I suspect the Evening Report will expand over time to become more analogous to the morning report, so we can give Garmin some slack here.

Anyway, back to the Sleep Coach.


Sleep Coach – the Supposed Background

Garmin would say that most people need between about 7 and 9 hours of sleep per day. As you get older, you typically need less sleep. Then, if you work out more and more intensely, you may well need more sleep than usual.

So, it seems plausible that Garmin, or any other tech company, could develop some sort of algorithm that looks at our patterns of sleep and then examines the short-term training loads we’ve placed on our bodies. This could be combined with a dash of HRV to determine how our body is coping with those training stresses and the stresses of everyday life too.


How Garmin Determines Your Daily Sleep Need

Garmin uses these five factors: age, daily and longer-term activity levels, recent sleep history, naps taken, and heart rate variability (HRV). Some algorithmic “magic sauce” is applied, and an adjustment factor is applied to your generic personal sleep need. For example, your normal need could be 8 hours, but that marathon you raced today bumped it up by 30 minutes.

The initial calculation actually happens in the morning and is adjusted based on your activity and naps during the day. The recommended amount of sleep should always be between 7 and 9 hours a day. Garmin goes as far as to say that if you need more sleep, it should come from naps.


The sleep Baseline

Q: What is my sleep baseline according to Garmin?

A: It’s 8 hours for a young adult (under 35) and falls to 7.5 hours for adults over 65


Garmin considers both sporting activity and low-level activity, like simply walking. To have these activities accounted for, obviously, you have to wear your Garmin watch.

From what Garmin has written publicly about its own algorithm, it appears that only hard workouts can cause a significant increase to the sleep need. Here, ‘hard’ would be determined both by the intensity and duration of your sporting activity, but even then, that is placed in the context of your recent training. So, it’s more about whether your workout has been relatively hard.

A light or inactive day may only result in a slight lowering of your sleep needs.



When Garmin looks at your 3-day sleep history compared to its recommendations, it adds some more of its “magic sauce.” Thus, if you’ve recently had too little sleep or too much, that can be factored into tonight’s recommendations, with more weight placed on the most recent night’s sleep.


Garmin claims that naps are primarily light sleep and typically exclude REM and DEEP sleep stages.

Naps will only ever lower your nightly sleep need, longer naps are more so than shorter ones.

Nap Architecture, Nap architecture from infancy to older adulthood. The dimmed region represents extrapolated data. [,,,]
Q: Is Garmin the best Sleep Tracker?

A: Probably not but it’s generally good at correctly logging sleep metrics (excluding sleep stages). I’d trust tech like Oura and Eight Sleep more.

Take Out

So I hope you quickly skimmed through all of that and nodded along as you went. It sounds plausible, right?

Here are some confounding factors

  1. Garbage in – garbage out: Garmin’s raw HR should be about right for many people but less so for HRV. However, HR also needs the context of your HR effort zones which, from my experience, Garmin calculates incorrectly. Worse still if you have caffeine before intense sport, at least 50% of us will have elevated HR making our workout intensity seem higher than what it is.
  2. Sleep Stages – Deep and REM sleep are fundamental to physical and mental recovery. However, there is no watch that can accurately record these. If anyone tells you otherwise they are wrong! If you had 2 hours of deep sleep in a 6-hour sleep is that more impactful than 10 minutes of deep sleep in a 9-hour sleep? So you can see that truly knowing the real time spent in sleep stages is important. We just don’t have that information correctly in 2023.
  3. Naps – Naps, as far as I know, can and do follow regular sleep stage cycles and so can include DEEP sleep which often occurs near the start of sleep events in any case.
  4. Practicalities – Athletes may well need X amount of sleep more but they simply, physically can’t sleep the extra time.
  5. 7-9 hours – While that might be a general recommendation from several health bodies it is simply the case that there is not a magic number for you that can be determined by Garmin’s magic sauce. It could be 7 hours for a 35-year-old or it could be 9, it’s likely not the middle figure Garmin takes (8).
  6. Female? – Bad luck, most of the science hasn’t considered your potentially different needs.
  7. Perception is better than measurement. – Actually how you feel about how good your sleep was can be a pretty good assessment and similarly, your perception of your sleep needs can also be good. Garmin could incorporate perceived/subjective factors.

But hey, all those screens on your watch look pretty, right?

It’s not magic sauce. It’s smoke and mirrors.


Inconvenient Science

I challenge Garmin and the wider wellness industry to say why the opinions expressed here are wrong. I’m not a scientist but I can read and my 30 minutes of simple Googling of scientific sleep literature and talking to some mysterious people ‘who know’ very very strongly suggests to me sleep coaching technology in watches is only very loosely science-based. And if it’s not science-based then this non-scientist (me) can only conclude that it’s almost certainly wrong and based on faulty foundations.

Try these quotes from sleep research papers:

There is no magic number [for sleep duration]. Chaput et al (2018, peer reviewed)

and another

…Lack of females [study subjects]

…A one-size-fits-all approach to athlete sleep recommendations (e.g., 7–9 hours/night) is unlikely ideal for health and performance. We recommend an individualised approach that should consider the athlete’s perceived sleep needs.

Research is needed into the benefits of napping and sleep extension. Walsh et al. (2021, Sleep and the athlete: narrative review and 2021 expert consensus recommendation)

and this

..may be premature to ‘prescribe’ naps as a health enhancer…Mantua & Spencer (2017, Exploring the nap paradox)


Reader-Powered Content

This content is not sponsored. It’s mostly me behind the labour of love which is this site and I appreciate everyone who follows, subscribes or Buys Me A Coffee ❤️ Alternatively please buy the reviewed product from my partners. Thank you! FTC: Affiliate Disclosure: Links pay commission. As an Amazon Associate, I earn from qualifying purchases.

8 thoughts on “Garmin Sleep Coach – An Explainer

  1. Pffffff, fortunately. More people think…..
    I have banned (sort of) the data from my Fenix.
    The RR (respiration rate) is another feature I thought was ‘questionable’. In correctness and usability.
    It’s way off!!!
    The nice thing is that this is data one can check! By doing a 2nd registration with cadence. Using just 1 RR. In my case 4 strides in 5 out) Then dividing time by the cycle.
    I haven’t spent time on researching the feature’s value….

  2. If you want to understand sleep better, to be able to better decide whether the info tech companies are giving you is BS or not, I can highly recommend reading/listening to “Why We Sleep” by Matthew Walker (he’s a real Doctor with over 30 years of specific experience of researching sleep – so genuine scientific evidence and analysis from one of the world’s leading experts behind what’s in the book).

  3. Garbage in, garbage out – spot on.

    That’s how I feel about most “wellness features” these days. They all sound great on the box, but in reality it often means stringing up many different data points and turning them into a score or single word. It’s mostly an indication of what each vendor thinks is right and not reality.

    And I grew, if polar can ask me about my feelings after a workout and tailor that jbtk my training load, it makes a lot of sense to do the same for sleep. More often than not I feel great after a few hours of sleep and tired/exhausted after a presumably long sleep.

    It’s all to be taken with a grain of salt IMO. I find real data (e.g. HRV) far more valuable than most of those flashy features

  4. While I agree that sleep tracking by current gen wearables isn’t the best, I do believe it gives objective data that helps people better themselves and be more accountable. I generally find Garmin to be pretty accurate for sleep duration, and I use that data to help me with my sleep routine.

    1. yes,
      i think generally the sleep TACKING pice is done well enough in the sense that what is recorded reflects reality. Except in the case of Sleep Stages where it is impossible (despte what you read). so time asleep, restlessness, wake time etc are ok

      however, this article is about the interplay with a forward-looking coach and the science that is out there. in a nutshell, the two don’t tie up. indeed science does not seem to ahev yet agreed/determined the things that Sleep Coach seems to want us to ebleive it has.

      check out the second of the links from Walsh…it’s an expert summary of a wide range of sleep studies…it’s about as good as a one stop shop as you’ll get.

Leave a Reply

Your email address will not be published. Required fields are marked *