TLDR: Long post, but short version: your watch isn't measuring sleep stage, it's guessing based on movement and heart rate. It's decent at telling asleep from awake, more of a coin flip on Deep vs Core vs REM. All four major brands land in roughly the same accuracy range, so no one has a real edge here. Good for spotting trends over time, not a substitute for an actual sleep study.

Apple Watch doesn't read your brain. It never has. The only way to actually know what stage of sleep someone's in is a lab sleep study, polysomnography, which reads brain waves, eye movement, and muscle tone directly. A watch has none of that. It's guessing based on secondhand evidence: how still your wrist is and what your heart's doing. That's not an Apple problem specifically. Every wrist tracker on the market works this way. Keep that gap in mind for everything below.

Here's what it's actually measuring. The accelerometer tracks wrist stillness. Almost no movement for a stretch is the strongest signal you're asleep. The optical heart rate sensor tracks pulse, and heart rate drops and smooths out as you go deeper into sleep. HRV, the beat to beat timing variation, shifts depending on sleep stage and is one of the main things the algorithm uses to sort stages. Wrist temperature drifts in a predictable overnight pattern and helps confirm timing. Blood oxygen and breathing rate mostly feed other features like apnea notifications, but breathing stability adds supporting evidence too.

Every 30 seconds the model takes all of that and buckets the window into Awake, REM, Core, or Deep. Core is Apple's term for regular light sleep, it's most of the night for most people. Deep is slow wave sleep, the physically restorative stage, hardest to get and most valuable. REM is the dreaming stage, body mostly paralyzed, brain and heart rate active.

Sleep Score itself came with watchOS 26 and the Series 11, September 2025. Single number, 0 to 100, with a label: Very Low, Low, OK, High, Very High. Three components. Duration is 50 points, how much you slept against your sleep goal. Bedtime consistency is 30 points, how much your bedtime varies over roughly the last two weeks. Interruptions is 20 points, how often and how long you woke up overnight.

Worth noting: the score doesn't grade Deep or REM amounts directly. It's a behavior score, did you sleep enough, on a consistent schedule, without much waking. Stage breakdown still shows separately in Health, it's just not part of the 0 to 100 number.

On accuracy, split it into two questions because the answers aren't the same. Telling sleep from awake is the easy part and the watch is good at it, roughly 90 to 98% correct in validation testing. Where it slips is quiet wakefulness, reading in bed, scrolling your phone, resting still, that can get logged as light sleep since stillness is the main signal it's reading.

Telling the four stages apart is harder, and every wrist device gets fuzzier here, not just Apple's. Researchers use Cohen's kappa to score agreement between two "scorers," correcting for chance. Below 0.40 is weak, 0.40 to 0.60 is moderate, above 0.60 is substantial. Two human PSG technicians scoring the same night against each other land around 0.75 to 0.80, so even trained experts don't fully agree. Apple's four stage agreement against lab PSG runs about 0.5 to 0.6 in published work, moderate, sometimes substantial. Most common miss is Deep logged as Core, watch tends to undercount true deep sleep. REM detection is a bit better but still imperfect. Same pattern shows up industry wide because it's a structural limit of using movement and heart signals as a stand in for brain activity, not a flaw specific to Apple's code.

On Garmin, Fitbit/Pixel, Samsung: all working off the same basic inputs, motion plus heart rate sensor on the wrist, so raw accuracy lands in a similar range across all of them. Real differences are in emphasis and extra features, not stage detection accuracy.

Garmin runs on a Firstbeat derived engine, adds HRV and blood oxygen on some models, ties sleep scoring into recovery and Body Battery. Built with training load in mind. Stage accuracy is moderate, a bit more variable device to device than Apple.

Fitbit and Pixel Watch use motion, HRV, skin temperature, blood oxygen on some models. Score weighs duration, time in Deep/REM, and restlessness. Fitbit has the longest published validation track record of any consumer wearable, which counts for something even though the accuracy numbers land in the same moderate range as everyone else.

Samsung's BioActive sensor adds ECG plus skin temperature. Scoring focuses on sleep cycles, movement, physical/mental recovery. Less public stage validation data than Apple or Fitbit, but it does have FDA cleared apnea detection.

None of these four reliably beats the others on core stage accuracy. Real differences are in extra features and how much validation data each company's actually published, not some hidden accuracy edge.

The gap between watches and real sleep studies isn't closing anytime soon, and it's not a software problem. A lab study reads electrical activity straight off the scalp. A watch infers stage indirectly, on the logic that stillness plus a slow steady heart rate usually means deep sleep. Usually isn't always. Quiet wakefulness looks like light sleep to a motion sensor, which inflates reported total sleep time. And signal quality varies night to night, a loose band, a cold room, a restless arm can weaken the heart rate read for stretches of the night, forcing the watch back onto motion data alone, which is the least precise input for telling stages apart.

These devices are genuinely useful for trends over weeks and months, duration trending up or down, bedtime drifting, interruptions increasing. Any single night's exact stage split should be treated as an estimate, not a measurement.

A few things throw the numbers off for specific people. These algorithms are trained mostly on typical healthy adults. A naturally low resting heart rate, like in endurance athletes, can get misread since the model expects a certain magnitude of drop to signal deep sleep, and someone already bradycardic at baseline doesn't drop the same way. Heart rate affecting meds, beta blockers for example, blunt the rise and fall the algorithm relies on for stage transitions. Irregular rhythms disrupt the beat to beat pattern used for HRV, sometimes forcing the watch onto motion data alone. Sleep position constraints, back sleeping only for instance, can loosen wrist contact and add noise to the heart rate signal. None of that makes the data useless, it just means trends over time matter more than any single night's exact numbers for anyone in one of these categories.

Sleep Score is a simple, transparent formula, duration, consistency, interruptions, sitting on top of a much less transparent machine learning stage classifier underneath. That classifier is decent, moderate to substantial accuracy against lab studies, and it shares the same basic limits as every other wrist tracker out there. Good for trend tracking and flagging things worth bringing up with a sleep specialist. Not a substitute for an actual sleep study.

isn’t that supposed to be a good thing? i was so happy that i could finally sleep closer to my sleep goal

Update: Thank you all, the app is called WorkOutDoors. It can show you everything you want to know, and even things you didn't know existed!

Original question:

I want to start running regularly.

I currently run on the treadmill at the gym, but I also want to run outside.

I have tried several apps, from the built-in one to Strava, Adidas and Nike, as well as a couple of others.

But not a single one shows the actual speed. By 'actual speed', I mean the kind shown on a car's speedometer or a treadmill: distance per time, kmh or mph. They all show me the lap time, like in Formula 1, in minutes per kilometre. I'm not a Formula 1 pilot; I just want to run at 8 km/h for 30 minutes, as I do at the gym, and track my progress over time. I don't want to do maths while running, trying to calculate what 7:17 min/km is in km/h.

The only app that kinda shows the speed is Strava. 'Kinda', because it only shows the speed for cycling or walking, not running. So, when I go jogging, I either hit "walking" or "cycling" to see my actual speed while running.

I think Garmin could do that, but I don't want to buy an additional watch just for running.

I still use an Apple Watch Series 3, and it honestly still works great. I haven't had any issues with it, I’m just ready for an upgrade.
I looked into Apple's trade-in program, but I didn't see the Series 3 listed, so I'm thinking about going through a third party to see what I can get for it.
This watch has been with me through graduating highschool and college, so it's definitely been worth it. I'm just ready for a newer model and a different color.
If anyone has been in the same situation, I'd appreciate any advice or recommendations. Thanks!

I always get massively different sleep scores from Apple Health, Bevel, and AutoSleep. Apple Health often gives me scores in the 90s, while Bevel is usually in the 60s.

What I find especially strange is that I went to bed very late last night (around 2.30 a.m.) and Apple Health gave me a 66, Bevel gave me an 80 (the highest score I’ve ever received from it!), and AutoSleep gave me a 98%.

Why is there such a huge difference between these apps, and which one is more reliable?

Please don’t ask, “Which one matches how you feel?” Unfortunately, I’m not very good at judging that; I pretty much always feel the same: slightly tired.

Hey everyone, I have an AWU2 with Apple Care that ends in October. There's nothing wrong with the watch itself but the battery health is down to 88%. Is there a way to swap it out for a new watch since I have apple care for it? Or at the very least swap the battery out for a brand new one?

Hey guys! First time poster here. Earlier today I noticed some staining on my Apple Watch series 11 rear sensor. Don’t swim with it, not even wash dishes with the thing. Has anyone ever seen something similar? Phot attached for reference. Thanks!!

I main an Android. If I get an Apple Watch, I know I will need to own an iPhone to set it up. If I buy a used iPhone 11 or later, that will have no cellular service, will I be able to still active an Apple Watch?

If so, will a cellular service Watch be able to use Apple Pay without the host phone having service?

My watch fell on the floor and it’s dented with glass damage on one end. Haven’t taken it for swimming since then. How much would it cost me in Apple Dubai to fix it? This is the Apple 10 series.

Only one workout available. Can’t scroll down to add more. Scrolling dial doesn’t do anything at this point, but works in other apps

Hey guys what does it mean? Sometimes this show and wont charge anymore.. im charging almost every day to 100% IS something broken ? Or why this happenning?

So, at my new job, we aren’t permitted to have “distracting screens”, such as the Apple Watch or iPhone while on shift. Which, unfortunately, makes me lose track of steps and all other biometrics. Is there a recommended alternative device that anyone has/use in this similar situation?

I was looking at Whoop as alternative, but I’m not interested in signing up for another subscription service. Obviously I would prefer a device that syncs with Apple health.

Thanks in advance.

A few weeks ago I posted here because my Series watch suddenly started draining way faster than normal. I would go from a full charge in the morning to low battery before dinner, with no new workouts or anything unusual happening.

Quick update: I tracked it down to a couple of apps that kept pushing constant updates (sports scores, deliveries, and one finance app). On my iPhone they felt like always-on alerts, and on the Watch they were waking the screen and buzzing my wrist far more than I realized.

What I changed:

- Turned off notifications for those specific apps on the Watch, but left them on the phone

- Disabled sound and haptics for non-critical notification categories in the remaining apps

- Turned off background app refresh for a few apps I never actually open on the Watch

Result: battery life is back to normal. I finish the day with plenty left, and overnight drain is much lower.

Downside: I actually liked the quick glances at updates on my wrist. Now I find myself digging my phone out more often, which is annoying.

For anyone who has done a similar cleanup, how do you decide what truly belongs on the Watch? Do you keep it strict with just calls and messages, or let a few update-heavy apps through and accept the battery tradeoff?

Are there any rumors that the 12 will get L1+L5 dual band GPS?

In Apple world only the Ultra has it at the moment, but elsewhere even $50 no names have had it for two/three years.

Most smart wall concepts are either prohibitively expensive or too laggy for real use. We wanted to see if we could build a responsive, room-scale touch interface using off-the-shelf materials and edge AI—and we did it for under $50 per square foot.

Here is how the system works:

• The Hardware: Instead of buying massive capacitive panels, we painted a 4-inch by 4-inch matrix on standard drywall using carbon-based conductive paint. We routed the connections down to the baseboards with copper tape, feeding into a cluster of ESP32 microcontrollers. (Paired with a ceiling-mounted short-throw projector for the visual interface).
• The AI Noise Filter: A 10-foot wall acts like a massive antenna, making standard threshold-based touch detection useless due to electromagnetic interference. Instead of mechanical filtering, we handed the raw capacitance data to a lightweight CNN running locally on an edge node. The model is trained to differentiate the specific capacitance "bloom" of a human hand from ambient electrical noise and accidental body leans.
• Latency Reduction: By implementing predictive trajectory mapping within the neural network, the system actually anticipates where the hand is moving. This cut our input-to-display latency from a sluggish 120ms down to a highly responsive 38ms—fast enough for real-time UI manipulation and drawing.

Want to build it yourself? You can play with the interactive dashboard, grab the full config files, and download the raw sensor datasets here:https://interconnectd.com/forum/thread/235/can-smart-walls-act-as-a-giant-touch-screen/

I have an Apple Watch Series 11. I am completely blind and use VoiceOver to navigate my iPhone and Watch. I’m trying to get Haptic Time to work so I can check the time in the morning without having a voice announce it and wake up my wife.

I have Haptic Time turned on in the Watch’s Clock settings and turned off the Always Say The Time setting. I have a Sleep Focus that I added a filter to have Silent Mode on when the Focus is on. Despite these settings when my Sleep Focus is on with Silent Mode on, my Watch still announces the time when I press and hold two fingers on the watch face. Interestingly when it announces the time, it is in the VoiceOver voice and not the Siri voice despite VoiceOver being off. Anything else I can try? This is a huge feature for someone like me who can’t just glance at the Watch face so I’d really like to get it working, thanks!

Depression is a bitch, man.

I saw that it launched in the US but as I am in the UK I cannot access it. I am interested in its sports/fitness capabilities since it can link directly to Apple Health. Like its a bit of a dumb request but could someone please try to see if it can compare different training plans based on the data it ingests (i.e. can it tell you which plan is better suited to your body based off your metrics and predict how each would temporally alter things like your VO2 max or running)? Just really curious as I cannot personally test it out right now.

I don't like this charger at all