Apple Watch Series 12 vs Series 11
Series 12 keeps the same 42mm and 46mm case sizes as Series 11 but replaces the optical heart rate sensor with a new Health Sensing System that measures continuously every five seconds throughout the day, adds a Readiness app, upgrades to the S11 chip, and toughens the aluminium glass. The ceramic case option returns for the first time since Series 5.
The questions here are simple: if you already own a Series 11, is Series 12 worth upgrading to? And if you’re buying your first Apple Watch, does the Series 11 at a discount still make sense?
For full testing and specs, see the Series 12 specifications and Series 11 specifications.
Series 12 vs Series 11 specs
| Spec | Apple Watch Series 12 | Apple Watch Series 11 |
|---|---|---|
| Processor | S11 SiP | S10 SiP |
| Heart rate sensor | New Health Sensing System, every 5 seconds all day | Optical, 3rd gen, periodic sampling |
| HRV measurement | Up to 24x more frequent; RMSSD and SDNN both exposed; Recovery HRV and overall HRV | Overnight HRV only; RMSSD only |
| Readiness | Yes, 0–10 daily score | No |
| Vitals app | Daytime and overnight views | Overnight only |
| Apple Intelligence | Yes (Siri AI, Audio Intelligence) | No |
| GNSS | Precision L1 (GPS, GLONASS, Galileo, QZSS, BeiDou) | L1 (GPS, GLONASS, Galileo, QZSS, BeiDou) |
| Glass (aluminium) | Ceramic Shield 2, 60% tougher than Series 11 | Ion-X with ceramic coating |
| Ceramic case option | Yes (pearl white, night blue) | No |
| Aluminium finishes | Dark bronze, black, light gold, space gray | Jet Black, Silver, Rose Gold, Space Grey |
| Titanium finishes | Natural, radiant gold | Natural, Gold, Slate |
| Battery, Low Power Mode | Up to 38 hours | Up to 36 hours |
| Battery, outdoor workout | Up to 10 hours | Up to 8 hours |
| 15-minute charge | 12 hours of use | 8 hours of use |
| Improved calorie estimates | Yes (from continuous HR data) | No |
| Launch price | From $399 / £369 | From $399 / £369 / €449 |
Case sizes (42mm/46mm), everyday battery life (24 hours), cellular (5G RedCap), Wi-Fi, Bluetooth, NFC, ECG, SpO2, skin temperature, water temperature, water resistance (50m), storage (64GB) and display brightness (2,000 nits) are unchanged from Series 11.
The Health Sensing System is the standout change
The shift from periodic heart rate sampling to continuous measurement every five seconds is the most meaningful hardware difference. The sensor has been redesigned: the old design used four circular photodiode windows; the new design uses eight windows with double photodiodes in each, roughly sixteen photodiode elements in total. Larger, more power-efficient green LEDs replace the infrared LEDs previously used for background HR, and ECG electrode surface area increased by 24%. Background heart rate recording switched from infrared to green LEDs, which is what enables always-on continuous sampling without the battery penalty that would previously have been prohibitive.
On Series 11, heart rate is recorded at intervals except during workouts. On Series 12 it runs all day, which gives the Vitals app and Readiness score more data to work from.
HRV on Series 11 is measured overnight using RMSSD only in Apple’s own app, though the underlying beat-to-beat data supporting both RMSSD and SDNN has always been available to developers via HealthKit. Series 12 measures HRV up to 24 times more often and, for the first time, surfaces RMSSD alongside SDNN directly in Apple’s own app, splitting the output into two distinct variants: Recovery HRV, which uses RMSSD for short-term daily stress and readiness signals, and overall HRV, which uses SDNN for a longer-term picture of cardiovascular health.
Readiness
Readiness is a new app that combines activity, training load, vitals and sleep into a single 0–10 score with a plain-English recommendation: Recover, Pace Yourself, Ready, or Go For It. It updates throughout the day as new data arrives. For endurance athletes who currently use third-party recovery apps such as Correlate or Cinder on their Series 11, Readiness replaces the core function of those apps natively.
Glass and case options
Ceramic Shield 2 on aluminium Series 12 is rated 60% tougher than the Ion-X glass on Series 11. The ceramic case option, last available on Series 5 in 2019, returns in pearl white and night blue.
Should you upgrade?
Series 11 still makes sense if
- You use a chest strap for training and don’t rely on wrist-based heart rate accuracy.
- You have no interest in Readiness, continuous HRV, or Apple Intelligence.
- Series 11 is available at a meaningful discount after Series 12’s launch.
It is worth noting that Series 11 owners who update to watchOS 27 will get Siri AI, the new Steps complication, improved step count algorithms, perimenopause and menopause support in Cycle Tracking, Workout Buddy without iPhone nearby, and Check In without buying new hardware. The hardware-exclusive features on Series 12 are the Health Sensing System, Readiness, continuous HR and HRV, Audio Intelligence, and the battery improvements.
Series 12 makes more sense if
- You rely on wrist-based heart rate and want the most accurate continuous reading available.
- You want a native daily readiness score without a third-party app.
- You want Apple Intelligence on your watch.
- You train with intensity and want daytime HRV and vitals tracking, not just overnight.
- You are buying new rather than upgrading from Series 11.
Coming from an older Series watch than Series 11? See the Apple Watch Series 12 upgrade guide for a full generation-by-generation decision.
Apple Watch Series 12
Smart sport watch
RRP from $399
£369, €449
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Get it nowOrder now – Apple Watch Series 12 Also sold direct by
Apple Watch Ultra 4
GPS adventure watch
RRP from $799
£749, €TBC
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Get it nowOrder now – Apple Watch Ultra 4 Also sold direct byAlso considering Apple Watch Ultra 4?
If you are a Series 11 owner who races Ironman or events over 14 hours, the Apple Watch Ultra 4 is worth factoring into this decision. Its GPS outdoor workout battery rises to 18 hours on Ultra 4, clearing the Ironman cutoff without Low Power Mode for the first time. Series 12’s outdoor workout battery is 10 hours, which does not help slower Ironman finishers any more than Series 11 did. The price gap is $400. If endurance battery is the reason you are considering an upgrade, Ultra 4 is the watch that actually closes it. See the Ultra 4 vs Ultra 3 comparison for the full detail, or the Ultra 4 vs Series 12 comparison if you’re weighing this year’s two current models directly.
Quick answers
Does Series 12 have a bigger battery than Series 11?
Everyday battery life is unchanged at 24 hours. Low Power Mode rises to 38 hours. The outdoor workout figure rises to 10 hours from 8, and a 15-minute charge now delivers 12 hours of use, up from 8 hours on Series 11.
What is the Health Sensing System?
The Health Sensing System is a redesigned optical and electrical heart sensor on Series 12. The old design used four circular photodiode windows; the new design uses eight windows with double photodiodes in each. ECG electrode surface area increased by 24%; background heart rate switched from infrared to green LEDs and now samples every 5 seconds. HRV is measured up to 24 times more frequently, and Series 12 surfaces RMSSD alongside SDNN in Apple’s own app for the first time; both have always been derivable from the underlying data via HealthKit. Apple uses RMSSD for Recovery HRV and SDNN for its other HRV measurements.
What is the Readiness app?
Readiness analyses recent activity, training load, vitals and sleep to produce a daily 0–10 score with a recommendation: Recover, Pace Yourself, Ready, or Go For It. It updates throughout the day and requires Apple Watch Series 12 or Ultra 4.
Last Updated on 8 October 2026 by tfk the5krunner
Small things I always use
- Garmin 90-degree charging adapter: Charges your Garmin from any USB-C cable. Essential when travelling. I use one.
- Body Glide: The blue anti-chafe stick swimmers and runners carry. I use it.
- Speedo earplugs: Fewer ear infections and no cold-water dizziness. I use them.
- Dryrobe Advance: My winter changing robe for open-water swims. I use one. A cheaper option is the AONYIYI changing robe.
- Maurten: Race fuel that stays easy on the stomach. I use them.
- Beet It Sport nitrate shots: Beetroot shots I take in the days before a race. I use them.
- Garmin charging puck: The quickest way to top up before a session. I use one.
- Injinji: Toe socks that stop rubbing, so you run more. I use them.
- Ultimate toe protectors: Stop black toenails on long runs. They work. I use them.
- Compressport R2 v2 calf sleeves: My calf sleeves of choice. I use them.
- Cellucor C4: My pre-workout before hard sessions.
- TPU tubes: Schwalbe Aerothan, Tubolito and Pirelli SmarTube. Light, tiny spares. I use all three.
- G8 insoles: Adjustable insoles that are good. I use them.
- Cycplus Cube: A 97g electric pump that gets a road tyre rideable in two minutes. I carry one. 5% off with code THE5KRUNNER.
Watches and sensors
- Polar H10: My daily driver for waking HRV.
- Polar Verity Sense: My backup arm-worn HR sensor.
- Nomad bedside charger: Charges my iPhone and Apple Watch overnight. I use it, and many of their bands.
- Train.Red: The best muscle oxygen sensor I’ve used.
- Tymewear: Accurate heart rate and reliable ventilatory zones. I use it to pace endurance rides over an hour.
- Garmin Forerunner 970: A pro-grade triathlon watch. I use this.
- Apple Watch Ultra 4: My daily smartwatch. No phone needed on rides.
- Garmin Fenix 9 Pro: I’ve just bought one.
On the bike
- Continental GP5000 for everyday riding, and Aero 111 on the front for special occasions.
- Helmets: Specialized S-Works Evade 3 for road riding, and Rudy Project Wing for TT-style races. I use both.
- Ravemen FR300: A front light that mounts under your Garmin or Wahoo. I use one.
- Wahoo TRACKR Radar: I use it on one bike and Varia on the other. They perform the same.
- Garmin Varia RTL515: Radar that warns you of cars from behind. I use this model.
- Wahoo ELEMNT Roam 3: The bike computer that’s easy to use. I use mine on most rides.
- Favero Assioma Pro RS2: Accurate power pedals that swap easily between bikes. I use this model.
Home and indoor training
- NPE Runn: Makes my basic treadmill smart, sending more accurate speed and distance to my watch and Zwift. I use it.
- Google Wifi: Keeps Zwift connected in my pain cave. I use it.
- Apple TV 4K: Zwift on the big screen. I use two.
- Google Nest Doorbell (wired, 2nd gen): My video doorbell, running in both Google Home and Apple Home. I use it.
Health, recovery and sleep
- FreeStyle Libre 3 Plus: Shows how my blood sugar responds to diet.
- hDrop: Measures my sweat loss in summer and indoors.
- Fourth Frontier Zone: Checks my heart under load in hard sessions.
- Oura Ring 5: My partner’s recovery tracker of choice.
- Eight Sleep: A cooling mattress cover my partner and I use nightly.
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tfk is the founder and author of the5krunner, an independent endurance sports technology publication. With 20 years of hands-on testing of GPS watches and wearables, and competing in triathlons at an international age-group level, tfk provides in-depth expert analysis of fitness technology for serious athletes and endurance sport competitors. See the gear tfk uses. ID
Has this article changed around the GPS differences between Apple Watch 11 and 12?
yes
So both run the same GPS? I only ask as deciding between the two and lesser gps accuracy in the series 12 compared to series 11 would be a deal breaker for the 12.
no they are different.
awu4 is certainly better
Thanks for reply – so is the Apple Watch series 12 a downgrade on the series 11 GPS as originally reported, equivalent of an upgrade?
no.
GLONASS is inaccurate, or can be. getting rid of it does or can increase overall accuracy. garmin fenix 9 pro does this