Apple Watch Ultra 4 vs Ultra 3: What’s Changed
Ultra 4 keeps the same 49mm titanium case as Ultra 3 but gains a new S11 chip, meaningfully longer battery life and a new Readiness app. The display, dimensions, satellite connectivity and durability ratings are unchanged.
The questions here are simple: if you already own an Ultra 3, is Ultra 4 worth upgrading to? And if you’re buying your first Ultra, does the discounted Ultra 3 still make sense?
For full testing and specs, see the Apple Watch Ultra 3 review, Ultra 4 specifications and Ultra 3 specifications.
What changed?
| Spec | Apple Watch Ultra 4 | Apple Watch Ultra 3 |
|---|---|---|
| Processor | S11 SiP | S10 SiP |
| Apple Intelligence | Yes (Siri AI, Audio Intelligence) | No |
| Battery, normal use | Up to 50 hours | Up to 42 hours |
| Battery, Low Power Mode | Up to 84 hours | Up to 72 hours |
| Battery, outdoor workout | Up to 18 hours | Up to 14 hours |
| Extended Workout mode | Up to 25 hours | Not available |
| Max Extended Workout mode | Up to 45 hours | Not available |
| 15-minute charge | 18 hours normal use | 12 hours normal use |
| Readiness app | Yes | No |
| High-frequency background HR | Yes | No |
| Recovery HRV | Yes | No |
| Weight | 63.0g (natural), 63.1g (black) | 61.6g (natural), 61.8g (black) |
| GNSS constellations | GPS, Galileo, QZSS, BeiDou | GPS, GLONASS, Galileo, QZSS, BeiDou |
| Launch price | $799 / £749 / €899 | $799 / £799 / €899 |
Case size (49mm), display (LTPO3 OLED, 1,245 sq mm, 3,000 nits), materials (Grade 5 titanium, sapphire crystal), water resistance (100m, EN13319 to 40m), satellite connectivity, Wi-Fi 4, Bluetooth 5.3, NFC and storage (64GB) are all unchanged.
Battery life is the standout improvement
The jump from 42 to 50 hours in normal use is the single most practically significant change. Ultra 3’s 14-hour GPS workout limit meant a full Ironman required Low Power Mode. Ultra 4’s 18-hour outdoor workout figure clears that without restriction. Extended Workout and Max Extended Workout modes push further still for ultramarathon and multi-stage events, though at the cost of metrics and alerts.
For triathletes and ultra-endurance athletes, this is a genuine hardware reason to upgrade.
The S11 chip and Apple Intelligence
The S11 brings Apple Intelligence features: a new conversational Siri AI, Audio Intelligence (including Live Rewind, Siri Recap, and Sound Recognition), and the Readiness app, which sits separately from the existing Vitals app and focuses on recovery and readiness to train. High-frequency background heart rate tracking and Recovery HRV are also new, both dependent on the S11. Siri AI launches in English only and is not initially available in the EU.
One thing to check: GLONASS
Apple’s Ultra 4 spec sheet lists GPS, Galileo, QZSS and BeiDou for GNSS, dropping GLONASS, which was listed for Ultra 3. Whether this reflects a hardware change, a chipset decision or a specification update is not confirmed. The practical effect on GPS accuracy is unlikely to be significant in most environments, but it is a specification difference worth noting for anyone who tracks it.
Garmin has recently made a similar decision with the satellite modes on its Fenix 9 Pro, also dropping GLONASS in some circumstances. It is also unclear there if Garmin uses a new GNSS chipset; what is known is that GLONASS is less accurate in several scenarios, and that’s why the constellation is dropped – to INCREASE accuracy.
Should you upgrade?
Ultra 3 still makes sense if
- Your events stay under 14 hours and battery life isn’t a limiting factor.
- You have no interest in Apple Intelligence features or the Readiness app. (Requires iPhone 15 Pro or above)
- Ultra 3 is available at a meaningful discount after Ultra 4’s launch.
Ultra 4 makes more sense if
- You race Ironman or ultra-endurance events and want GPS workout battery without Low Power Mode.
- You want the Readiness app, Recovery HRV or high-frequency background heart rate tracking.
- You want Apple Intelligence on your watch.
- You are buying new rather than upgrading from Ultra 3.
Quick answers
Is Ultra 4 much bigger than Ultra 3?
Case dimensions are identical at 49mm x 44mm x 12mm. Ultra 4 is 1.3–1.4g heavier than Ultra 3, which is unlikely to be noticeable on the wrist.
Can Ultra 4 do a full Ironman without Low Power Mode?
Yes. Apple claims up to 18 hours of outdoor workout battery on Ultra 4, which covers the Ironman cutoff of 17 hours without needing Low Power Mode. Ultra 3’s 14-hour GPS figure required Low Power Mode for events longer than that.
What is the Readiness app?
Readiness is a new app on watchOS 27, distinct from the existing Vitals app, that tracks recovery and readiness to train. It requires Apple Watch Series 12 or Ultra 4 and the S11 chip. It is not available on earlier Apple Watch models.
Does Ultra 4 still have GLONASS?
Apple’s Ultra 4 spec sheet lists GPS, Galileo, QZSS, and BeiDou but not GLONASS, which appeared on the Ultra 3 spec sheet. Apple has not confirmed whether this is a hardware or documentation change.
Last Updated on 9 September 2026 by the5krunner
My favourite kit and nutrition
- Garmin Fenix 9 Pro — I’ve just bought one.
- Injinji – Runners protect your toes. Avoid discomfort and minor injury. Run more. Run faster. I use them.
- Garmin 90-degree charging adapter — A small keyring adapter you can use anywhere. Essential when away. I use one.
- Garmin charging puck — the fastest and most reliable way to top up your Garmin before a session. I use one.
- Ravemen FR300 — Front light that mounts directly under your Garmin or Wahoo head unit. Keeps your bars clean and your beam pointed where it matters. I use one.
- Body Glide – The blue anti-chafe stick that all swimmers and many runners use. I use it.
- Maurten — The race nutrition trusted by elite athletes. Gels and drink mixes engineered to be easy on the stomach. I use them.
- Garmin Varia RTL515 — A radar rear light that alerts you to vehicles approaching from behind. Pairs with your Edge or Wahoo. I use this model.
- Favero Assioma Pro RS2 — The power-meter pedals most serious cyclists choose. Accurate, easy to move between bikes. I use this model.
- Garmin Forerunner 970 — A serious choice for a pro-grade triathlon watch. I use this.
- Polar H10 — My daily driver for accurate, waking HRV readings.
- Wahoo ELEMNT Roam 3 — The bike computer that has the feature Garmin lacks: usability. I use mine on most rides.
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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. ID
Will some of the new announcements come to the AWU 3: mainly Readiness, HRV over a dedicated app and inclusion in Vitals?
idk, maybe not because they rely on the increased hrv polling rate for accuracy