Apple Watch Ultra 4 same case, two-day battery, better heart data

What is new about the Apple Watch Ultra 4?

Almost everything that changed is inside or underneath. Apple announced the Ultra 4 on 9 September 2026 and kept the case from the Ultra 3: the same 49 mm titanium body, flat sapphire front, orange Action button and knurled Digital Crown. Expert Reviews puts it bluntly: set it next to an Ultra 3 and you would be hard pressed to tell them apart. This first look covers the black titanium case with the Translucent Black Ocean Band, the version sold under this ASIN.

Flip it over and the story changes. Apple calls the new sensor array the Health Sensing System. Expert Reviews describes larger ECG electrodes, photodiodes arranged in a ring and bigger, more efficient green LEDs. The practical result, according to Apple, is a background heart rate reading every five seconds and heart rate variability (HRV) readings as often as every five minutes. Apple quotes 60 times more frequent background heart rate readings and 24 times more frequent HRV readings than the Ultra 3.

That data feeds a new Readiness score, worked out each morning from recent activity, vitals and sleep, then adjusted during the day. There is also a new S11 chip, a new step counting model that Apple claims is the most accurate of any smartwatch, and Audio Intelligence features such as Sound Recognition and Live Rewind. Some of those, Apple notes, arrive in beta later in 2026.

How big is it, and how will it wear?

Big. Apple lists the case at 49 mm tall, 44 mm wide and 12 mm deep, with the black titanium version weighing 63.1 grams before the strap. Apple says it fits wrists from 130 mm to 210 mm. There is only one size, so anyone with a slim wrist should try one in a shop before committing.

The display is the largest Apple makes: 422 by 514 pixels, 3,000 nits at peak and down to 1 nit for dark rooms. The Ocean Band is a stretchy rubber strap with a titanium buckle, and Expert Reviews notes that the wetsuit extension costs extra.

How long does the battery last?

This is the headline. Apple quotes up to 50 hours of normal use, 84 hours in Low Power Mode, 18 hours of outdoor workout tracking, 25 hours in Extended Workout and 45 hours in the new Max Extended Workout mode. Engadget notes the gain over the Ultra 3, and Expert Reviews points out that it is the longest battery life Apple has claimed for any watch.

Independent results line up with the claim. Expert Reviews reports two full days with the always on display, sleep tracking and around three hours of workouts, charging on the morning of the third day. Charging is quicker too: Apple says 15 minutes adds up to 18 hours of normal use, and charging to 80% takes about 45 minutes.

How well does it track health and workouts?

Expert Reviews compared it with a chest strap and found it matched for peak and average heart rate, and reports quicker response when the pace picked up in interval work. Tom's Guide, which had found the Ultra 3's readings sketchy at times, compared it with a chest strap and an Oura Ring 5 and describes the Ultra 4 as pretty much spot on. GPS is dual frequency, and Apple lists running power, cadence, Race Route, Pacer and offline maps with custom routes.

For water, Apple rates the Ultra 4 to 100 m under ISO 22810:2010 and certifies it to EN13319 for recreational scuba to 40 m, with a depth gauge and water temperature sensor. There is satellite messaging for Emergency SOS, a siren and a torch on the Action button. Expert Reviews notes that the Readiness score has no history view yet, unlike Oura's equivalent.

Is it good value against its rivals?

The RRP is £749 on Apple's UK store, the same price as the Ultra 3 at launch, with cellular included. Expert Reviews lists the main rivals:

• Apple Watch Series 12: from £369. Same sensors, Readiness score and S11 chip, but an aluminium case, no Action button, no satellite messaging and a daily charge.
• Samsung Galaxy Watch Ultra 2: £649. Similar two to three day battery in Expert Reviews' testing, but it only works with Android phones.
• Garmin fenix 9: £859. Expert Reviews suggests it as the sports watch alternative for those who put training tools and stamina ahead of apps.

For an iPhone owner who wants the toughest Apple Watch and the longest battery, nothing else does what this does. If you mainly want the new health data, the Series 12 gets it for half the money.

What is the catch?

Three things. First, the design has not moved since 2022, so Ultra 3 owners get no visible change for their money. Second, it needs an iPhone 11 or later running iOS 27, so Android users should look elsewhere. Third, some of the promised features are not here yet: Live Rewind and Siri Recap arrive in beta later this year, and Expert Reviews lists the lack of dedicated stress tracking as a weakness.

It is also too new for a meaningful body of owner feedback. Early reviews are positive about the battery and heart rate accuracy, but long term reliability will take months to judge.

“The changes are on the back of the watch, not the front.”