is Garmin 965 Accurate? full report

Is The Garmin Forerunner 965 Accurate?

Answer: Accuracy is good to excellent.

More: Garmin Forerunner 965 Review – opinion and the negative bits

This article is a full-accuracy report based on selections from a month of workouts with non-beta firmware on the FR965. It looks at accuracy across various data types including GPS/GNSS, HRV, Sleep Stages, Elevation and HR.

TL;DR – Accuracy seems to be an incidental concern for Garmin. Sure, GPS/GNSS accuracy is now market-leading but it’s taken years to get to this point. Heart rate accuracy is hit-and-miss and person-dependant…you might be lucky, but I often wasn’t.

I’ll focus more on HR as that is where most of the problems are. Let’s get cracking with some charts from each test and a quick sentence or two to highlight the key takeaway from each.

HR Accuracy Run

This is a 90-minute tempo run at a pretty consistent pace on a warm day. I’ll blame the rigid nylon band for Garmin’s discrepancy at the start, otherwise, it’s pretty good.


Here are some intervals of varying lengths on hard, flat ground. This is not good enough by Garmin (green) that’s beaten by WHOOP and the Apple Watch. It’s just wrong when it counts. Again, this is not quite good enough from Garmin.



This is a 20-ish minute threshold run on hard ground. Garmin does well here and is better than Apple.


I think these were meant to be 5ish minute VO2max efforts but turned out to be a bit half-hearted. Once again, Garmin tracks too highly at the start and misses the peak towards the end.

This is one of the nicer runs on the pavement with WHOOP thrown into the mix. All are great this time around.


HR Accuracy Bike

This ride is in the Surrey Hills and often includes rough roads. The purple line is the FR965 and there are clearly some discrepancies fro it to the others, although most of them seem to be at the cake stop! There is under-reporting therefrom Garmin but I’d just about take this level of accuracy as a basic log of the ride and an input for load calculations (TRIMP). For any kind of race pacing it’s not good enough, at least not on this day.


This ride is a 1-hour tempo ride on smooth roads. This is not really acceptable from Garmin and Apple Watch is superior albeit with a wobbly moment at 1hr 50.


This is another Surrey Hills ride but at a relatively hard, steady effort level for 2 and a half hours over smoother-than-average roads for the area. Garmin does a nice job here.



This is a super-easy one for Garmin on the Kickr indoor trainer. Nice job all around. When there’s no bouncing and wrist movement it’s easy to get accurate oHR.


HR Accuracy – Swim

Accuracy when swimming is troubling as Garmin’s HR curves always look plausible. Here is a typical example comprising a warmup, flat out 10 minutes and then  3x 2 lengths ramping up the intensity with paddles. The brown curve is the Polar OH1 and that is the one that is almost certainly correct even though on the very last length it flipped over on my biceps.

I haven’t yet completed any open-water swims with the FR965

Elevation Accuracy

These seem about right.

Note: Do this now. Walk outside your house and do a manual altitude calibration using the result from This value will be used in all future runs and rides starting from home.

Sleep and Sleep Stage Accuracy

I’ve been reading so much nonsense about this from just about everywhere on the internet. Device manufacturers, bloggers, reviewers, YouTubers, scientists, the lot.

Here I wore 4 of the leading devices almost every night for a month and then spent a couple of hours compiling a spreadsheet of the time in sleep stages. It was a thoroughly thankless task as it is patently obvious that these devices are random number generators. Or at least 3 of them are. One could be correct. None of them agrees…at all.

Garmin 965 shown

I shall say no more than to reiterate once again that the maximum possible accuracy for sleep stages on a watch vs polysomnography is 80%. Every single device will be less accurate than that. From a cursory look, you might guess that they are all a lot less accurate than 80%. Still, each of them produces very pretty sleep stage charts; that’s what you are paying for.

HRV Sleeping Accuracy

I’ve taken a waking HRV reading almost every morning for the last month with a Poalr H10 using HRV4Training. I’ve correlated it to the nightly average HRV for Garmin 965, Oura Ring and Apple Watch 7. Here you can see the best correlation with HRV is simply the number of hours I’ve trained for followed closely by the distance I’ve covered.

That said, this is a strange result and I would have expected at least one of the devices to show a 0.8-0.9 correlation. It is what it is. Even though I’m not comparing like with like, these measures should all correlate similarly assuming the base data is correct.

All that I can think has happened is that I’ve probably drunk more alcohol than I usually do (once a week rather than once a month!) and halfway through the month I started using another sleep gadget that definitely has me waking up feeling fresher but sleeping less – that may or may not impact HRV.

Anyway, the conclusion is that you can’t trust any of these gadgets to capture nightly HRV anywhere near accurately enough. In months gone by, Oura and the Apple Watch have returned much higher accuracy results


Image cut and pasted to remove unhelpful rows of data


Readiness To Train Accuracy

Many companies now produce readiness-to-train metrics.

There is no such thing defined as readiness to train, each time you see that phrase it means something different from one manufacturer to the next. It might be possible to compare one readiness number to another or to calculate which best correlates to ‘performance’.

Pace Accuracy

I’ve not specifically tested for this and I overrode the Garmin values with a Stryd footpod from day 1 as I was using the 965 as a training device and wanted that metric to be correct.

I did have the GAP pace on permanent display as well. That did not respond quickly enough to true changes in grade but once stabilised seemed OK.

Running Power Accuracy (Running Dynamics)

I’ve not specifically tested for this either. And, in any case, there’s nothing to compare it to that could be accepted as correct.

Garmin’s running power is certainly a usable training metric but will only be as accurate as the accuracy of the individual sensor inputs. You can get these inputs from sensors in a variety of locations on your body ie RD-POD, chest strap and now even fully from the FR965 itself. A calibrated foot pod is the best source if you want as much accuracy as you can get, the wrist as a source will likely be the worst.

955 Comparison shown for illustration

This link explains Garmin Running Power in detail and this link gives lots of test results for the FR955.

The bottom line is that there are two ‘correct’ methods of determining running power and each gives a significantly different result. Garmin and Polar use variations of one method and Apple, Coros and Stryd use variations of the other. The chart above clearly shows those similarities when looked at over data smoothed by 10s of seconds – runners looking to action 5s average power, or similar, will find very significant discrepancies between the different running power systems.


Garmin Running Power – An Explainer [2022]


GPS Accuracy

The Forerunner 965 has a battery-hungry GNSS (GPS) mode that uses every constellation of satellites AND two signal frequencies from each satellite. That means LOTS of available satellites and a way to determine individual satellite signal accuracy by looking at the time taken for the different signal frequencies to travel what should be the same distance, then eliminate the signals that have either bounced or refracted in the atmosphere. Even better, Garmin FR965 has a special SatIQ mode which powers up the super accurate mode only when it is needed.

As always, if you simply want a pretty picture of where you’ve been then just use the battery-friendly GPS-only mode. It’s fine for that purpose.

In practical terms, GPS accuracy impacts several aspects of your device

  • Instant running pace
  • The start and end times/positions of your Strava segments
  • Your actual track under trees and in built-up areas and mountainous areas – the track could be extremely inaccurate in those scenarios
  • Navigation
    • The accuracy of navigational prompts in those tricky areas of reception
    • The timeliness of the same navigational prompts. These will be (appear) delayed if you are either travelling fast or if the watch is underpowered.


GPS Accuracy – Open Water Swim

I’ve not yet braved the cold spring water to test this.

Open Water swimming should be easy for GPS as there will rarely be trees or canyon walls obscuring the satellite signal. Of course, those pesky satellite signals don’t travel underwater and that’s why many sports watch companies struggle with open water accuracy as specially modified algorithms are needed to avoid having a power-hungry beast continually searching to acquire signal.

Garmin’s history here is that they were initially producing ‘alright’ levels of accuracy. Then it ‘improved’ the algorithm and which just didn’t work ;-). Having fixed that a couple of years ago the result was market-leading. I’d expect that to be the case now on the FR965.

GPS Accuracy – Cycling

I expect that most of you will also have a bike computer. If that’s the case, Garmin lets you set the GPS accuracy level differently for each sport profile…just use GPS-only for all kinds of cycling on the watch and then whatever you want for your handlebar-based solution.

I didn’t cycle through mountainous passes but forests, open roads and urban canyons were all super-fine in max accuracy mode. Here are images from 3 different rides showing the general awesomeness apart from the 60m tunnel in Kingston…unsurprisingly there was no GPS signal to find in a tunnel.

GPS Accuracy – Running

I like this test, or at least I like the useful results it tends to produce rather than the monotony of running around the block to execute it! It exemplifies suburban running in the UK with minimal trees and houses that are probably too far away to make much of a negative difference to the GPS reception. Yet some devices struggle on this test. The killers are the sharp 90-degree bends and the need to stay on track on relatively long and straight pavements. I’ve given one of many examples of a corner, below, where Garmin just seems to nail this every time. The final image shows the Fr965 having a mini-wobbly in someone’s garden but that one slip-up is fine and only off-course by a couple of metres.

These are in max accuracy mode.


the FR965 scored an excellent 83% over a standard 10-mile test that I’ve put just about every GPS watch ever through. FR965 was nearly identical to the best-ever track from Epix 2 at 87% except the FR965 messed up one particularly long section where it ran parallel to where it should – other than that section if anything, it was very slightly superior to the Epix (it has later GPS firmware). The slip-up is likely due to the incorrect handling of signals that bounced off closeby buildings…ie precisely what multiband is supposed to correct for! Oh well.


Test methodology and FIT files are linked here.


Take Out

The current level of technology across the key sports watch companies – Garmin, Apple, Coros, Polar and Suunto is the best it has ever been. If implemented properly each vendor could produce the good to excellent results we’ve seen here from Garmin.

GPS accuracy can still be improved but it must surely be about as good now as it is ever going to get

oHR is never that great for me and I can’t be alone. Other reviewers and athletes clearly get better results than me but others get the same or worse than me. This is the area that Garmin and the industry now need to focus their efforts on. That’s not just because we all want more accurate HR metrics but it is that HR is used to power pretty much all the physiology metrics and if it isn’t correct then all the physiology stuff we like to pore over will simply be wrong.

Resting HRV is the basis of a mixed bag of metrics used across the industry. It should be mostly correct but often is just wrong as all the companies, including Garmin, apply a mixture of scientifically-grounded algorithmic tweaks and then some pseudo-made-up ones to give a nice-sounding metric like readiness to train.

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31 thoughts on “is Garmin 965 Accurate? full report

  1. You really are glutton for punishment testing these wrist optical HR during sport.

  2. Finally an accurate test. I am using this devices for so long and everyone saying that is so much accurate but my personal experience is far from it. I’m disappointed with the results that I’m getting in almost every aspect of the metrics and this test describes the problem

  3. I switched from a fr 935 to a fr 965. I had the 935 for 6 years and it was a fine watch.

    In 2 weeks I noticed the 965 isn’t any better than the 935 was in areas I find important. Gps on the 935 was fine, and it still is on the 965 although instant pace still isn’t very good.
    Ohr on the 935 didn’t work for me and on the 965 still doesn’t work for me.

    Sleep is still way of. I only look at sleepstart, time awake during the night and sleep end. Sleepstart starts to early (when I’m still watching a movie/series) when I’m awake for hours during the night it isn’t detected, and sleep end only ends when I get out of bed.

    The 965 produces a lot more data. Most take sleepscore into account, which is wrong, so most data is wrong. But I don’t care much. I’m not into over quantifying my life.

    Maps look nice, but navigation with breadcrumbmaps has been fine for over 10 years. Maps aren’t that clear on a small screen, so on difficult junctions you still have to stop and look really careful.

    The 935 display was fine. The 965 display looks great but since gestures don’t work that good it’s quite annoying. Especially when doing intensive intervals on a track. A quick look always result in looking at a black screen.

    The 965 is a fine replacement for my 935 which battery was almost dead and will serve me for 6 years again, I hope.

    I’m not disappointed in my new watch. Just a little bit in real progress made in 6 years time. But to be honest, I don’t know what new to expect and I know marketing wants to sell devices, so they come up with a lot of fluff.

  4. Hey, thanks for the no nonsense review. I like your style more than the others. Also the 5krunner part, I am a 5K type of runner my self, I don’t get those marathon people!

    I remember looking at your site some years ago when I bought the Suunto 5. Glad I found it again (it wan’t easy, perhaps because I was mostly looking at YT). So now I’m itching to replace the Suunto with something less straining on the eyes. OK, maybe just looking for a new toy if we’re honest. The thing that would most dissapoint me would be to get a new watch with worse GPS accuracy, so I’m happy to hear Garmin has finally caught up and is now as good as my old Suunto (or perhaps a bit better still). HR on the Suunto is very bad when running, but it’s fine when resting/sleeping, so hoping the 965 will be the same. I always use the Polar OH1 when running anyway. When it comes to sleep (and perhaps HRV), I totally agree, it’s all marketing. Looking at your month long test, one thing I noticed is that the Oura shows on average too little deep sleep. But yeah, it’s naive to expect this tech to resolve sleep stage. Those graphs sure look pretty though and I guess I’ll just go ahead and buy it, enjoy looking at them (and all the other numbers the watch produces) and try to discern any correlations with how I actually feel, only to once again realise there’s nothing tangible there:)

    Finally I am just a little worried about the visibility under sunlight thing, but I am guessing it won’t be a problem. I can see my Pixel 2XL just fine under the sun and that has 450nits of brightness, something tells me the 965 got to be brighter than that (between 500 and 1000 I would guess), so hopefully it will all be good. I’ll come back with an update if I remember.

    1. ty
      brightness is fine for me.
      super bright june sunshine might cause some problems but there is a brightness control. perhaps polarised lenses could be a problem too

      the 965 is definitely a bigger screen than the S5 🙂

      1. Yep, 65% bigger to be exact! And infinitely brighter , should be quite an improvement.
        I avoid running under intense sun anyway, so (polarized or not) glasses not applicable.
        Still not available where I live, hopefully in a couple of weeks for the new toy 🙂

    2. Brightness isn’t the problem. The watch is bright enough.

      Becoming bright is the problem. Gestures aren’t working very well. They are either not registered or it takes quite some time before the screen turns on.

      On long runs, this might not be a big issue. Doing fast track work this is rather annoying. A quick glance at your watch just shows a black screen.

      Also, late in the evening when you want a quick look at the time, this cannot be done without a gesture or aod on.
      But aod let you have a light on your wrist all the time. I find that annoying.

      Also when you are in bed, just outside your defined sleeptime, moving your arm can result in turning the brightness on. Which is quite bright in a dark bedroom.

      The screen looks absolutely great. But the usage comes with annoyances I never had on a mips display.

      1. Thanks for the feedback Leo.
        Yes, I had read about the gesture complaints, conflicting reports I have to say.
        5K is my mode for now, but I am thinking about starting some track work too. Can’t you have it always on for track work? This is something I don’t understand to be honest, isn’t there an option to have it always on at the highest brightness setting when out in the sun?

        As for the night, I see, I hadn’t thought about that. Oh well, guess I’ll have aod off and just tap it or gesture. As for sleeping before my defined (i.e. “desired”) sleep times, never happens!

      2. Afaik, it is not possible to have full brightness in aod all the time. The watch will dim after a few seconds and you have to use the gesture to turn up the brightness again. The dimmed display might be readable enough, depending on to lights outside.

        Yeh, sleep measurement is also very personal. Dcrainmaker claims to have no problems at all with sleep start and sleep end times. But he never says what he’s doing just before he goes to bed. He might be active making reviewmovies until late at night and is woken by the alarmclock and jumps out of bed immediately.

        My restingheartrate is fairly low (around 40bpm), so reading or watching a movie is easily mistaken for sleep. Also, most of the time I’m awake before the alarm.

        I just don’t value all those metrics (body battery, training readiness, etc) very high. At best they confirm what you already know about your body, or they only work for average Joe, or they are just marketing bs.

      3. hi
        ty for the comments

        brightness: yes, that sounds right. I don’t think its onerous that the gesture ups the brightness.
        dcr/wake/sleep – I think it’s unrealistic to expect tech to know if you are asleep when you are, for example, deliberately lying motionless in bed for whatever reason (which might even include reading)
        HRV readiness vs feel – I correlate how I feel with what readiness to train says (using HRV4T). they don’t correlate for me! I might just be more rubbish than others at mentally determining how ready I am to workout.

        marketing Bs: i think the convoluted readiness to train metrics are bs to quite a degree, possibly even to a very high degree of bs!!!. however the basic waking hrv changes to baseline are scientifically meaningful – those are correctly calculated by Garmin based on whatever raw data quality they input into the algo, however, Garmin then uses that number as an input to their proprietary bs algo. admittedly I still look at it!

      4. Hrv measuring with an optical heartrate monitor is a good way and the data that produces is sound. I understand the need to convert the number into something like, yes you can train, or no you must rest.

        Science isn’t clear or know it all, all the time. 5 to 10 years ago we all had to watch our resting heartrate to know our recovery. Now it is know there isn’t much correlation between them.

        But it’s fun the discuss about it. And I do know I present my observations and opinions somethimes a bit too strong. English is not my native language. And I’m dutch, I’m expected to be direct 😉

      5. I thought I had read that for proper HRV measurement one needs an ECG tpe of HR montor, not optical?

    3. OK, quick update one week (and 4 runs) after I got the watch. Color me impressed. Maybe I had low expectations, I was thinking that I am paying to get a hugely better screen experience and hopefully marginally better GPS and HR. The screen lived up to the expectations and yes it is easily visible under intense sun (though not quite as easily as MIP). Just waiting for a firmware to offer a more natural color palette. These “radioactive” greens and reds are annoying.

      For the HR measurement I had low expectations, as I said my Suunto was total rubbish and useless. But this is hugely better for me. In fact I got very close plots with the Polar OH1 connected to my S5 for 3 of my runs. And consequently identical average HR and max HR to within 3bpm (on two occasions it leveled for the last 10-15 sec of the final sprint while the OH1 kept climbing). The 4th time (today) I forgot to tighten the watch band (for the other 3 I had tightened it by one stop compared to my usual setting) and as a result there was a slight wobble in the first half of the run.
      Overall it looks at the very least useable on holidays where I usually forget to bring the OH1. It would be interesting to test it on some intervals.

      The GPS impressed me even more. Granted I have only run 4 times on the same circuit (twice sunny, twice cloudy and rainy) but it is hugely better than the S5 that has me routinely cutting into buildings and trees. No such case so far wth the 965, in fact it has me usually on the right side of the track. I am excited to see such accuracy.

      HRV also seems reasonable (small flactuations correlating to me overtraining or not, so far). Other devices I had tried (fitbit) were varying way to much night from night and correlation was weaker. We’ll see. Earlier today and about an hour after my reluctant, not easy run, it notified me that I was too “stressed” (97%) while trying to clean something on the floor. The stress metric uses HRV (intraday polling I guess, as opposed to the overnight where we get an average). I am guessing that was the correct call, I was feeling knackered and not in a good way, I guess my HRV must had plummeted and it called it corectly. Maybe. Either way I listed to it and sat down to chill for a few mins!

      Sleep, well who knows, it seems OK overall, but with regard to sleep stages probably not that good, need more time to verify how bad it is.

      Overall very happy, no regrets at all, this is the most signifcant upgrade of any electronic device I’ve upgraded before I think!

  5. Thanks both. OK, I guess it’s the case then that full brightness always on is not possible, perhaps 2/3 (?) which could be enough in most cases and if not, I’ll have to see for myself how onerous the gesture is. It’s also possible Garmin can improve its sensibility with a firmware update I guess.
    I just saw a video from the quantified scientist that suggests Garmin has room for improvement in sleep stages tracking since his tests sleeping in a lab for a few days show the latest Apple watches doing a pretty good job apparently. Which again will depend on the individual, but still it may be that we’ll have to wait a bit more for a watch that does most things fairly well in one package.

    1. i do not think QS does sleep tests in a lab
      he used to but i think he just compares to a headband.

      see the above comments on the general uselessness of sleep stages in the consumer world.

      afaik, the ONLY properly performed science into consumer grade tech’s sleep stages was from oura. iirc their latest algorithm scored 75% against polysomnography which i doubt any other consumer tech would get close to. the algorithm used for that is still only in beta and i think only with the latest gen oura ring

      1. He (TQS) posted the lab test yesterday. Apple 8 scored 80%+ if I remember correcly (for him at least).

      2. ok ty
        yes i just skimmed though that ( it’s probably one of the best reviewer tests I’ve seen. N=3 over 4 nights in a lab. so that beats my n=1 over 30 nights at home!
        he correctly points out some of the limitations at the end, however!
        1. i don’t think he mentioned the number of polysomnography scorers. I’d assume 1. The scorers add in a human element and there is often (usually) variance between the scorers!!
        2. polysomnography can only score 80% accuracy.
        3. the n=1 or n=3 could be a material problem. he tries to eliminate sex differences (fair enough) and points out skin tone differences. however there could be MANY other compounding errors from, for example, people with more extreme typical HRV levels.

        again, i think only the Oura study has true merit.

        I’m probably going to keep doing these tests just to keep reiterating that sleep stages are probably wrong! sadly it’s one of the key features that quite a few people look for.

      3. Yes, sorry, I hastily referred to the average correlation for the 4 sleep stages he quotes as the 80%+ score. Yes overall I agree with you, as I said in my first post, it is unrealistic to believe these devices can monitor sleep stages with any certainty and of course it will vary from person to person. That said, even if Apple gets a 70% score and Garmin gets 50%, that’s something Garmin can improve on and would make a lot of the wellness/training readiness numbers it produces more trustworthy. So at some point in the future we can have a training watch that is decent in most areas of interest.
        As for Oura, if it’s the most accurate (though I know you are referring to the beta version), then you are not getting enough deep sleep I think, your average seems to be less than an hour:)

  6. The Stamina metric is interesting I think. I did a 63.3k hilly ultra at the weekend & looking at the metric afterwards, it hit zero around the 53k mark & that was right about the time I “adopted” a walk/run strategy to get to the finish. Thankfully when I got over the last hill I was able to run the last ~2.5k to the finish line so having zero stamina doesn’t mean you’ve become incapable of running.

    1. agreed.
      it is quite dynamic in how it works and the inputs it takes.

      thus it needs to get an idea of your true long term endurance abilities – 53k vs 63k.
      it should be even better next time around

  7. As a Stryd user, how do you work around the issue, that native power cannot be disabled and Stryd can not be chosen as native power source?

    You will, I suppose, have two sets of power data to work with. Is that problematic?

    1. hey thomas
      Garmin Running Power CAN be disabled on the 965. I recently found that option squirrelled away somewhere, tho the chances of anyone, including me, ever finding it again in garmin’s labyrinthine menu system is close to zero

      polar, coros and suunto do not, afaik, have the same ability.

      1. I’m never leaving Garmin 🙂

        Still unsure if this is worth the upgrade from Fenix 6 Pro. They way I see it, all I get is a pretty screen. We have it on sale i Denmark for just 475£, though, at the moment.

        I consider waiting for an Epix 3 that hopefully will get Qi and ECG.

  8. thanks for the review. I think the same as you, I have had two Garmin 245, an Amazfit and now a Galaxy Watch 4 and the results are random. The one that disappointed me the most was the Garmin. He miscounted steps, floors, heart rate and sleep. The worst thing was in swimming, I couldn’t get the lengths or style right (I missed by a lot!). In your experience, excluding Apple, which watch is more reliable for swimming? Do the new Garmin ones improve anything on that?

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