Apple Watch Series 12 Vs. Ultra 4: Which New Smartwatch Is Right For You?

Apple unveiled its latest Apple Watch models at its September 9 event alongside the iPhone 18 Pro and iPhone Duo. The Series 12 starts at $399, while the Apple Watch Ultra 4 starts at $799. Both run Apple's new S11 chip, use the new Health Sensing System, and introduce a new readiness score, just like Whoop and Oura trackers. Beyond that, you'd be hard-pressed to spot many changes compared to last year's Apple Watch Series 11 and Ultra 3. Both of the new smartwatches go on sale September 18 after pre-orders opened on September 9.

Almost everything Apple introduced in its keynote (via YouTube) applies to both watches. The heart rate sensing, readiness, Live Rewind, the redesigned Health app, and Siri AI on the wrist. The $400 between them buys battery life, titanium, satellite communications, and a pair of workout modes built for events that run longer than a day. So if you're looking to buy one of the new models, here's what separates them, and who should actually pay the difference.

Both watches run on the new S11 processor, which Apple calls its most powerful wearable chip, and it's the first meaningful upgrade to the Apple Watch chip in years. Alongside it, both get Apple's new Health Sensing System that powers almost every new fitness feature. Those new fitness features are also powered by new optical and electrical heart sensors, which enable a heart rate reading every five seconds rather than only during workouts, and HRV measured as often as every five minutes, which is 24 times more frequently than before. Apple claims the most accurate heart rate sensing in a wearable on both, based on a study of over 1,000 participants against rival devices.

Apple's new Readiness score also appears across the two smartwatches, taking recent activity, training load, vitals, and sleep score and returns a 0-10 score each day with one of four recommendations: Recover, Pace Yourself, Ready, or Go For It. The scoring algorithm also came out of Apple's Heart and Movement Study. Both also claim the most accurate step tracking of any smartwatch, and both get the new Steps complication so you can easily keep track of them.

Audio Intelligence is a brand new set of features that arrives on both watches, too. Live Rewind shows the last 15 seconds of a conversation as text after a double press of the Digital Crown, Siri Recap summarizes conversations afterward, and Sound Recognition flags sirens, alarms, and doorbells. Live Rewind and Siri Recap will arrive in beta later this year, but will require the new watches. Siri AI comes to the Series 11 and Ultra with the watchOS 27 software update (which will roll out to most other Apple Watches), as does the redesigned Health app with its Longevity tab, Health Age readout, and at-home movement evaluations.

Most differences between the two watches are similar to previous years, with battery life being the widest gap. The Series 12 offers the same 24 hours of everyday use as the Series 11, with 10 hours of outdoor workout tracking and a 15-minute charge that returns 12 hours. The Ultra 4 will last for up to 50 hours of everyday use — 84 hours in Low Power Mode — and gains 18 hours of juice from the same 15-minute charge. The Ultra 4 has two new workout tracking modes: Extended Workout, which tracks activities with full GPS and heart rate for 25 hours, and Max Extended Workout, stretching runs, walks, and hikes to 45 hours while still taking a GPS reading every second. The Ultra 4 also claims the most accurate on-device GPS in a sports watch, a claim Apple doesn't make for the Series 12.

Satellite remains a feature limited to the Ultra. Emergency SOS, Find My, and Messages over satellite without an iPhone arrived on the Ultra 3, and return this year. There are no new satellite features on the Ultra 4, so you don't need to upgrade from last year's model for connectivity reasons. Satellite connectivity still comes free for two years from activation through Globalstar, though Apple has been saying that for years and has never begun to charge users.

The physical body and design are another big difference between the watches. The Series 12 comes in 42mm and 46mm sizes, in aluminum, titanium, and, for the first time since 2020, ceramic in pearl white and night blue. The aluminum models get Apple's Ceramic Shield 2 display, which is reportedly 60% tougher than the Series 11's Ion-X glass. The Ultra 4 comes in only one material but with two color options (natural or black titanium), a larger case, and a brighter display. The straps are made in different sizes, but you can use them interchangeably, even if they're not a perfect fit.

You should buy the Ultra 4 if your smartwatch needs to regularly survive for longer than a day and a night away from a charger. 50 hours of everyday use versus 24 hours is something you'll notice on a daily basis. Ultramarathoners and multi-day hikers will benefit from the longer battery life, the new Max Extended Workout mode, and satellite messaging. Since there's no way to get these features on older models, you'll need to buy the Ultra 4 — unless you only want satellite messaging, which does come on the Ultra 3.

Everyone else should look towards the more affordable Series 12. It comes with the same new processor, the same updated health sensors, the same readiness score, and the same Audio Intelligence features, which cover nearly everything Apple announced for the new watches. 24 hours of battery life should still get you through a day and a night of sleep tracking, provided you charge the watch back up while you shower.

The ceramic case is a finish rather than a feature, but it is priced higher. Who should spend the extra $400? Those who train for long events or work outdoors, which is where the longer battery life and satellite connectivity come in handy. Otherwise, buy the Series 12 and keep the difference, because most of the new features are available across both watches.