Apple Watch Ultra 4

What’s new: the heart sensors and readiness

The reason Ultra 4 exists next to Ultra 3 is the Health Sensing System. It’s hardware, so Ultra 3 can’t get it in a software update: Apple redesigned the optical and electrical heart sensors, made the green LEDs bigger, and gave the S11 chip the job of sampling far more often.

Heart rate. Ultra 4 checks your heart rate in the background every five seconds, all day, whether or not you’re working out. Apple says that’s 60× more often than Ultra 3, which works out to roughly once every five minutes on the older watch (Apple doesn’t state that interval itself). A new complication can keep the live number on your watch face.

Heart rate variability. HRV is sampled as often as every five minutes, day and night, which Apple calls 24× more often than Ultra 3, or roughly once every two hours on the older watch. Ultra 4 separates Recovery HRV, a day-to-day stress and recovery signal it compares with your baseline overnight, from overall HRV. Vitals now has a daytime view as well as the overnight one.

Readiness. Each morning you get a 0–10 score and a one-line call: Recover, Pace Yourself, Ready or Go For It. It’s built from your recent activity, training load, vitals and Sleep score, it updates after a hard session or a change in your vitals, and it shows which factor is moving the number. Apple says it built the model with its exercise scientists and physicians using data from the Apple Heart and Movement Study. In practice it answers one question, push or ease off, without five charts.

Apple says the new sensors beat “leading wearables” in an internal study of 1,000+ participants. We haven’t seen the study’s method.

Sleep

Ultra 4 tracks sleep stages, gives you a Sleep score that also feeds readiness, and can notify you of possible sleep apnea where Apple offers it. Five minutes on the charger buys about 10 hours of sleep tracking, Apple says.

The screen is Ultra 3’s

Apple didn’t change the display. It’s the same 3,000-nit Always-On LTPO3 Retina under flat sapphire: 422 × 514 pixels at 326 ppi, down to 1 nit in the dark, with wide-angle OLEDs. Night Mode turns the Modular Ultra, Wayfinder and Orienteering faces red after dark.

Always On refreshes at 1Hz, so the seconds hand keeps moving with your wrist down. Ultra 3 introduced that; Ultra 2 and earlier updated Always On about once a minute. If you’re coming from Ultra 1, which peaks at 2,000 nits on a 410 × 502 screen, the difference is obvious. From Ultra 3 there’s nothing new to see here.

Battery and charging

This is the second reason to upgrade. Apple’s ratings:

Mode	Ultra 4
Normal use	Up to 50 hours
Low Power Mode	Up to 84 hours
Outdoor workout	Up to 18 hours
Extended Workout	Up to 25 hours
Max Extended Workout	Up to 45 hours (outdoor run, walk or hike, GPS every second)
Fast charge	About 80% in 45 minutes; 15 minutes for up to 18 hours; 5 minutes for up to 10 hours of sleep tracking

Ultra 3 is rated for 42 hours of normal use and 72 in Low Power Mode, so a long weekend without the charger is now realistic. It’s still a watch you charge every couple of days, though. If you need GPS running for days at a time, look at a Garmin expedition watch, which trades the bright screen and Apple’s apps for endurance. The Magnetic Fast Charger to USB-C cable (1m) comes in the box.

Built for water, dirt and bad days

These are the things that make it an Ultra rather than a Series watch:

• Water and diving: water resistant to 100m (WR100 under ISO 22810:2010) and certified to EN 13319 for recreational scuba to 40m. Dive apps such as Oceanic+ open automatically at 1m, and GPS marks where you went in and came out.
• Dust and knocks: IP6X dust protection, and tested to a list of MIL-STD-810H methods: altitude, heat and cold, temperature shock, immersion, freeze and thaw, freezing rain, shock and vibration.
• Action Button, siren and flashlight: big physical controls that work with gloves and wet hands. Hold the Action Button and the siren carries up to 600 feet (180 meters), Apple says.
• Satellite: Emergency SOS, Messages and Find My work with no cell signal. Ultra 1 doesn’t have this.
• Navigation: compass with bearing, incline, elevation and coordinates; Backtrack; waypoints, including automatic ones where you last had a cell signal; offline maps with custom routes. Topographic maps and curated hikes in all 63 U.S. national parks are U.S.-only.

Fall Detection, Crash Detection, Emergency SOS, Check In, Last Emergency Call and noise monitoring are on every current Apple Watch, not just the Ultra.

Workouts it tracks

• Running: custom workouts, training load and effort, heart-rate zones, VO2 max, Race Route, Pacer and Precision Start on the Action Button, plus form metrics: cadence, stride length, ground contact time, vertical oscillation and running power. It detects tracks automatically.
• Hiking: the compass, waypoint, Backtrack and offline-map tools above, plus elevation alerts.
• Cycling: speed, elevation and distance; Bluetooth power meters; Functional Threshold Power; cadence, power and power zones; a Live Activity on your iPhone.
• Swimming: pool and open-water modes, interval workouts with haptic cues, automatic sets and stroke detection (kickboard included), SWOLF and water temperature.
• Diving: recreational dives to 40m with current and maximum depth, dive time and water temperature.
• Also listed: skiing, snowboarding, outdoor rowing, paddling and golf.

That’s what Ultra 4 can track, not proof it’s the best tool for every sport. Garmin’s sport lists run longer.

Software: Siri AI and Audio Intelligence

Ultra 4 ships with watchOS 27. The same update reaches Series 9 or later, SE 3 and Ultra 2 or later, all paired with an iPhone 11 or SE 2 or newer on iOS 27, so the software alone isn’t a reason to buy.

What is S11-only is Audio Intelligence: Sound Recognition, automatic Shazam, Live Rewind and Siri Recap. Apple says recordings aren’t stored, processing runs through the Secure Enclave, it doesn’t identify who is speaking, Live Rewind chimes even in silent mode, and saved snippets and summaries are end-to-end encrypted in iCloud. Live Rewind and Siri Recap are betas due in late 2026. Siri AI arrives in English first and won’t be available in the EU at first.

Bands, payments and what’s in the box

Ultra 4 uses Apple’s Ultra band fitting, not a standard 22mm quick-release, and the box includes one band. This year’s sport bands are the Trail Loop (dark umber, sand, burgundy), the Alpine Loop (desert, dark olive, burgundy) and a translucent silicone Ocean Band (gray, kelp, black). The Hermès Ultra 4 with the Grand H face is sold separately. Apple Pay and GymKit are built in.

Apple says Ultra 4 is made with 45% recycled content, including all of the titanium in the case and 100% recycled cobalt and 95% recycled lithium in the battery.

Ultra 4 or Series 12?

Both have the Health Sensing System. The Ultra is the bigger, brighter, longer-lasting and tougher one:

Spec	Ultra 4	Series 12
Case	49mm, Grade 5 titanium	42mm or 46mm aluminum
Peak brightness	3,000 nits	2,000 nits
Action Button, siren, 40m dive, satellite	Yes	No
Normal-use battery	Up to 50 hours	24-hour class
Max Extended Workout	Up to 45 hours	Not offered

Series 12 vs Ultra 4 goes through the rest.

Price

Ultra 4 starts at $799 in the US. Education pricing, Apple’s monthly plan (its example is $24.99 a month for 24 months), the Hermès edition and your band choice all change what you pay. Every Ultra 4 is the cellular model, A3579.