Apple Watch Series 12 and Ultra 4 Add New Health Sensing System

Apple has announced the Apple Watch Series 12 and Apple Watch Ultra 4, both built around a new Health Sensing System and the S11 chip. The Series 12 starts at $399 and the Ultra 4 starts at $799, keeping the same starting prices as their predecessors.

Pre-orders opened Tuesday, September 9, with availability beginning Friday, September 18.

The new Health Sensing System

The largest shared upgrade is Apple's new Health Sensing System, which combines redesigned optical and electrical heart sensors with larger, more power-efficient green LEDs. Apple says it provides the most accurate heart rate sensing of any wearable it tested, a claim it says was validated by an Apple Watch Heart Rate Accuracy Study that compared the watch against other wearables using an ECG test strap as a reference.

Background heart rate readings are now taken every five seconds, which Apple says is 60 times more often than on the Apple Watch Series 11. Heart rate variability can be measured as often as every five minutes, which Apple describes as 24 times more frequently than before. A new complication lets users view their real-time heart rate throughout the day.

Apple has also improved the surface at the bottom of the watch to make ECG readings more consistent.

Readiness

The additional sensor data powers a new Readiness feature, which gives users a score based on recent activity, sleep, vitals, and recovery data. The score updates during the day rather than only in the morning.

S11 chip and Audio Intelligence

Both watches use Apple's new S11 chip, which enables Siri AI and a set of Audio Intelligence features including Sound Recognition, a faster Shazam, Live Rewind, and Siri Recap. Apple says some of the Audio Intelligence features will arrive later in 2026 rather than at launch, and that they will initially support English only.

Battery life

The Apple Watch Ultra 4 sees the larger battery gain, rising to up to 50 hours from the 42 hours on the Apple Watch Ultra 3, with up to 45 hours of extended workout tracking. Apple did not increase the quoted battery life on the Series 12.

Materials and durability

The aluminum Series 12 now uses Ceramic Shield 2, which Apple says is 60 percent tougher than the Ion-X glass used on the aluminum Series 11. Apple also brought back ceramic Series 12 models, offered in white and blue at a higher price.

Software

Both watches run watchOS 27, which reaches existing devices as a free update on September 14. watchOS 27 includes Siri AI in English, a dynamic app grid, a tap gesture for the Smart Stack, and Workout Buddy without a nearby iPhone.

What did not make the cut

Despite pre-launch speculation, the Series 12 and Ultra 4 do not add a blood glucose sensor, and rumored Touch ID did not materialize.

Reports before the event suggested blood pressure or hypertension notifications could be a feature this year, though it is not yet clear how Apple is positioning that capability in this generation, and buyers should confirm details against Apple's specifications.

Apple also did not raise the starting price on either model.

Pricing and availability

The Apple Watch Series 12 starts at $399 and the Apple Watch Ultra 4 starts at $799.

Both became available for pre-order on September 9, with retail availability beginning Friday, September 18 in the United States, the United Kingdom, the UAE, and dozens of additional markets.