Apple is giving its most capable smartwatch a substantial health and fitness upgrade. The company today unveiled the Apple Watch Ultra 4, adding a new Health Sensing System, the S11 chip, more frequent heart-rate and HRV measurements, a new readiness score, and significantly longer battery life.

The new Apple Watch Ultra 4 retains the rugged titanium design aimed at athletes and outdoor users, but Apple is increasingly positioning the Ultra as a comprehensive health, fitness, and safety device rather than simply an adventure-focused smartwatch. It starts at $799 in the U.S., with preorders opening September 9 and availability beginning September 18.

The Ultra 4 is available in natural and black titanium finishes. Apple is also introducing new colors for its Trail Loop, Alpine Loop, and Ocean Band accessories, while the Apple Watch Hermès Ultra 4 gets its own new Grand H titanium band and Fathom and Wonder watch face.

A new Health Sensing System sits at the center of the Ultra 4

The biggest change is inside the watch. Apple Watch Ultra 4 introduces a new Health Sensing System built around redesigned optical and electrical heart sensors, with Apple claiming it delivers the most accurate heart-rate sensing in a wearable.

Apple says a study involving more than 1,000 participants compared the new Apple Watch sensing system against leading wearables and found Apple Watch had the highest accuracy across the devices tested. The new system also uses larger, power-efficient green LEDs and measures heart rate every five seconds throughout the day.

That higher-frequency sensing feeds into several new features. Heart-rate variability, or HRV, can now be measured up to 24 times more frequently, with Apple separating the data into Recovery HRV and overall HRV to provide different views of short-term recovery and broader cardiovascular health.

Apple is also adding a new daytime vitals view, allowing users to switch between overnight and daytime measurements. The idea is to make changes in physiological metrics visible during the day rather than waiting for the next night’s sleep data.

The Ultra 4 also introduces Readiness, a new 0-to-10 score designed to help users decide how hard they should push themselves on a given day. It considers recent activity, training load, vitals, and sleep, then provides one of four recommendations: Recover, Pace Yourself, Ready, or Go For It.

Importantly, the score isn’t static. Readiness can update during the day as new information arrives, such as after an intense workout or a change in daytime vitals. Apple says the underlying algorithm was developed using data from the Apple Heart and Movement Study in collaboration with exercise scientists and physicians.

The Ultra 4 can last up to 50 hours

Battery life is another major area of improvement.

Apple Watch Ultra 4 can now deliver up to 50 hours of everyday battery life, compared with the previous generation‘s lower endurance. Low Power Mode stretches that figure to as much as 84 hours.

Charging has also been improved. Apple says a 15-minute charge can provide up to 18 hours of additional battery life, making it easier to recover a substantial amount of battery during a short charging session.

For serious outdoor activities, Apple is introducing Extended Workout mode. It provides up to 25 hours of outdoor workout tracking with full GPS and heart-rate readings, representing a 25 percent improvement over the previous model.

There’s also a Max Extended Workout mode for even longer adventures. It can track outdoor runs, walks, and hikes for up to 45 hours while continuing to record GPS data every second. Apple says that’s typically enough to complete a 100-mile race.

More accurate steps and GPS

Apple is also rebuilding the Ultra’s pedometer system. New machine-learning algorithms running with the S11 chip are designed to improve distance measurements during indoor walking and running workouts while making all-day step counts more accurate.

Apple is going as far as calling the Ultra 4 the smartwatch with the most accurate step tracking. A new Steps complication also lets users see their step count directly from the watch face.

The company is similarly highlighting improvements to GPS accuracy, calling the Ultra 4’s on-device GPS the most accurate in a sports watch.

For outdoor athletes, that combination of more precise positioning, higher-frequency health measurements, and longer workout battery life could end up being more important than any individual new watchOS feature.

Apple is giving the Health app a major redesign

The Ultra 4’s new sensors also feed into a redesigned Health app coming to iPhone later this year.

The updated app will introduce a new Longevity tab that analyzes longer-term health data. One of the headline features is Health Age, which uses selected metrics to show how a user’s health measurements are tracking relative to their age.

Apple is also adding an Insights tab that will provide changing summaries across areas including heart health, sleep, readiness, fitness, vitals, and cycle tracking. The goal is to turn the growing amount of health data collected by Apple Watch into information that’s easier to understand and act on.

This is part of a broader push by Apple to combine its wearable sensors with Apple Intelligence rather than treating the Watch as an isolated fitness tracker.

Apple Intelligence comes to the Ultra 4

The S11 chip isn’t only about health sensing and performance. Apple says it also enables a new class of Audio Intelligence features coming later this year.

One example is Sound Recognition, which can alert people who are deaf or hard of hearing to sounds such as sirens, alarms, doorbells, or a baby crying, even when their iPhone isn’t nearby.

Apple is also introducing Live Rewind, which can help users recall something that was just said in a conversation, along with Siri Recap for summarizing information such as a personal training routine. Apple says these features are designed with privacy and security in mind, with Live Rewind and Siri Recap data end-to-end encrypted in the Siri app with iCloud syncing.

With watchOS 27, the Ultra 4 also gets a new version of Siri powered by Apple Intelligence. Siri AI can understand personal context and access broader world knowledge, allowing users to continue conversations directly from the wrist.

Siri AI will initially roll out as a beta with watchOS 27, starting September 14 for supported devices and languages.

watchOS 27 adds more ways to use the Ultra one-handed

The Ultra 4 also benefits from the broader watchOS 27 update.

Apple is adding a dynamic app grid that surfaces five Siri-suggested apps based on usage. Smart Stack suggestions can also appear when they are contextually relevant, such as showing a Parked Car suggestion in Maps or a birthday-related suggestion when appropriate.

A new single-handed tap gesture expands the Watch’s accessibility and usability options. Users can tap their index finger and thumb together to select a widget, while the existing double-tap gesture can be used to scroll through the Smart Stack.

Workout Buddy is also coming directly to Apple Watch when an iPhone isn’t nearby, while Cycle Tracking is gaining support for perimenopause and menopause.

New titanium finishes and bands

Apple Watch Ultra 4 comes in natural and black titanium, keeping the rugged design language that has defined the Ultra lineup.

Apple is refreshing its outdoor bands at the same time. Trail Loop is available in dark umber, sand, and burgundy, while Alpine Loop comes in desert, dark olive, and burgundy.

The Ocean Band is getting a more distinctive change, moving to a translucent silicone design offered in translucent gray, translucent kelp, and translucent black.

The Apple Watch Hermès Ultra 4 is also joining the lineup in natural titanium. Its new Grand H titanium band includes an extension mechanism designed to make it easier to adjust over a wetsuit, while the new Fathom and Wonder watch face lets users explore an animated representation of the ocean’s depths.

Apple Watch Ultra 4 price and availability

Apple Watch Ultra 4 starts at $799 in the U.S. and is available to preorder starting September 9. It will arrive in stores on September 18.

watchOS 27 arrives September 14 for Apple Watch Series 9 and later, Apple Watch SE 3, and Apple Watch Ultra 2 and later. The update requires an iPhone 11 or later, or an iPhone SE (2nd generation) or later, running the required software.

For Apple Watch Ultra users, the Ultra 4’s appeal isn’t simply that it is the newest and toughest Apple Watch. Apple is using the new generation to push the device further into continuous health monitoring, recovery tracking, endurance sports, and intelligent assistance.

The result is an Ultra that looks familiar on the outside but is considerably more ambitious underneath.