Apple Watch Series 12

What’s new: the Health Sensing System and readiness

Series 12 shares its big change with Ultra 4. The Health Sensing System is new hardware, with redesigned optical and electrical heart sensors and larger green LEDs, so Series 11 and SE 3 can’t get it in a software update.

Heart rate and HRV. Series 12 checks your heart rate in the background every five seconds, all day. Heart rate variability is sampled as often as every five minutes, which Apple says is up to 24× more often than the previous Series; working back from that, Series 11 sampled HRV roughly every two hours. Recovery HRV and overall HRV both show up in Vitals and the Heart Rate app, and Vitals now covers the day as well as the night.

Readiness. Every morning, Series 12 gives you a 0–10 score with one of four calls: Recover, Pace Yourself, Ready or Go For It. It’s built from your recent activity, training load, vitals and Sleep score, and it updates through the day. It’s the same feature Ultra 4 has, and it’s where all that extra heart data becomes useful: one call a day on whether to push or rest.

Apple says the new sensors beat “leading wearables” for heart-rate accuracy in its own study of more than 1,000 participants. That’s Apple’s claim, and we haven’t seen how the study was run.

Screen and case

The display is a wide-angle LTPO3 Always-On Retina: 374 × 446 pixels on the 42mm and 416 × 496 on the 46mm, both at 326 ppi, peaking at 2,000 nits and dimming to 1 nit. Always On refreshes once a second (1Hz), which arrived with Series 10 in 2024, so Series 10 and 11 owners won’t see a difference. Ultra 4 is the brighter watch, at 3,000 nits.

The case material decides the front glass, the weight and, for ceramic, a little of the size:

• Aluminum (dark bronze, black, light gold or space gray) is the lightest, from 31.5 to 39.5 grams for the case, and uses Ceramic Shield 2, which Apple calls tougher than any smartwatch glass.
• Titanium (radiant gold or natural) adds about four to six grams and swaps in a sapphire front crystal. The case is 3D-printed from 100% recycled titanium.
• Ceramic (pearl white or night blue) also gets sapphire, but it’s roughly ten to fourteen grams heavier than aluminum and slightly bigger: 43mm or 47mm tall and 9.85mm thick, against 9.7mm for the other two.

Battery and charging

Mode	Series 12
Normal use	Up to 24 hours
Low Power Mode	Up to 38 hours
Outdoor workout	Up to 10 hours
Fast charge	About 80% in 30 minutes; 15 minutes for up to 12 hours; 5 minutes for up to 10 hours of sleep tracking

The outdoor-workout rating is for a run with the heart-rate sensor on and no iPhone nearby. Apple says it’s 25% longer than on the previous model, which works out to about eight hours on Series 11. If your trips last days rather than hours, Ultra 4 is rated for 50 hours of normal use, 84 in Low Power Mode and 45 in Max Extended Workout.

Water and safety

Series 12 is water resistant to 50m and dust-rated IP6X. It’s built for swimming and snorkeling, with a depth gauge to 6m and a water-temperature sensor; scuba, waterskiing and high-speed water sports are out. Recreational diving to 40m (EN 13319) is an Ultra feature.

For emergencies you get Fall Detection, Crash Detection, Emergency SOS with international emergency calling, Check In and a flashlight. Satellite SOS and messaging stay on the Ultra.

Workouts and step tracking

Apple lists dedicated tools for running (including running power), hiking (with U.S. topographic maps and hikes in 63 national parks), cycling (Bluetooth accessories and Functional Threshold Power) and swimming (SWOLF and kickboard detection), plus a “More Workouts” list that runs from skiing and golf to HIIT and yoga. Workout Buddy now works on the watch itself when your iPhone isn’t nearby, over Wi-Fi or cellular, in English and Spanish; the full feature needs an Apple Intelligence-enabled iPhone.

Step counting gets a redesigned pedometer and a new Steps complication. Apple calls it the most accurate step tracking of any smartwatch, based on its own 1,000-step, video-checked test against leading smartwatches as of July 2026.

Software: watchOS 27, Siri AI and Audio Intelligence

watchOS 27 isn’t a Series 12 exclusive. It also runs on Series 9 or later, SE 3 and Ultra 2 or later, paired with an iPhone 11 or iPhone SE (2nd generation) or newer on iOS 27.

What needs S11 is Audio Intelligence: Sound Recognition, automatic Shazam, Live Rewind and Siri Recap. Live Rewind and Siri Recap are late-2026 betas that need an Apple Intelligence-enabled iPhone 16 or later (not iPhone 16e); they start in English and won’t be available in the EU at first. Siri AI is a watchOS 27 beta with the same English-first, not-yet-in-the-EU limits. watchOS 27 also adds a one-handed tap that opens a Smart Stack widget, alongside double tap and wrist flick.

Series 12, Ultra 4 or SE 3?

All three get watchOS 27 and have 64GB of storage. Here’s what separates them:

Spec	Series 12	Ultra 4	SE 3
Case	42mm or 46mm; aluminum, titanium or ceramic	49mm Grade 5 titanium	40mm or 44mm aluminum
Peak brightness	2,000 nits	3,000 nits	1,000 nits
Health Sensing System and readiness	Yes	Yes	No
ECG and Blood Oxygen	Yes	Yes	No
Action Button, satellite, 40m dive rating	No	Yes	No
Battery, normal use	Up to 24 hours	Up to 50 hours	Up to 18 hours
US starting price	$399	$799	$249

Series 12 vs Ultra 4 and SE 3 vs Series 12 go through each choice in detail, and Series 11 vs Series 12 covers the one-year upgrade.

Bands, payments and what’s in the box

Series 12 takes Apple’s standard watch bands, not a 22mm quick-release strap. This fall’s range adds new Sport Band and Sport Loop colors (two of the loops are plaid), Nike Sport bands in five new colors, a Milanese Loop in radiant gold or dark bronze and a Modern Buckle in a new woven material. Ceramic models come with a sand or navy Sport Band with a ceramic pin-and-tuck. Hermès Series 12 is a separate collection, in radiant gold titanium for the first time or in silver titanium, with a new Rocabar Club band.

Apple Pay (with a participating card issuer) and GymKit are built in. The box holds the watch, a band and a 1m Magnetic Fast Charger to USB-C cable. Apple says Series 12 is made with 40% recycled material, including 100% recycled aluminum in the aluminum cases.

Price

Series 12 starts at $399 in the US. Apple’s monthly-payment example is $11.99 a month for 24 months on a $399 42mm model, and education pricing, titanium, ceramic, cellular and the Hermès edition all change what you pay. Pre-orders opened on announcement day, and stores had it from 18 September 2026. Check the exact configuration on apple.com before you buy, since prices change.