Vanessa Hand Orellana/CNET
Pros & Cons
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2.5-day battery life with always-on display -
Up to 45 hours of workout tracking in Max Extended mode -
Readiness score adjusts throughout the day -
Health and recovery metrics aren’t locked behind a paywall
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Battery life still trails dedicated sports watches -
No Readiness score history or long-term trends -
49mm design can feel bulky for sleep tracking -
Audio Intelligence features still pending
The Apple Watch Ultra 4 is finally ready to join the big leagues in the dedicated sports watch category. It has a new processor and reengineered sensors that unlock more frequent health measurements, new recovery insights and AI-powered audio tools, all without having to pay for yet another monthly subscription. But the biggest reason to upgrade this year may be battery life. A larger battery combined with a more power-efficient processor delivers at least 10 hours more than its predecessor in my testing and more power-saving options for endurance athletes.
I’ve been putting the $799 Ultra 4 through its paces for a week, and while I’m still running (literally) more battery tests, I already have a pretty clear picture of where this watch shines.
Since the Ultra 4 and Series 12 share many of the same upgrades, you can find a deeper dive into the new processor, health sensors and WatchOS 27 features in my Series 12 review. In this story, I’m just focusing on what sets the Ultra 4 apart, which is a lot.
New sensors unlock more health data
At first glance, the Ultra 4 looks and feels familiar. But when I flipped it over, the difference was obvious. Compared with the dual ring of sensors on my Ultra 3, the Ultra 4’s array looks like a flower, with 32 electrodes resembling the thin petals of a gerbera daisy. The arrangement gives the electrodes more surface area to capture ECG readings. Apple also rearranged the green and infrared LEDs into a new, smaller circular cluster in the middle of the petals with smaller dots. Those redesigned sensors, combined with its new S11 processor, allow the Ultra 4 to take heart-rate readings every 5 seconds, compared with roughly every 5 minutes on previous models. The same goes for heart-rate variability, or HRV, which the watch can now measure every 5 minutes instead of just a few times throughout the day.
Readiness score
That increased sampling provides a more complete picture of what your heart is doing throughout the day, including moments outside of a workout, and helps unlock the new Readiness score. It’s Apple’s measure of how ready (or not) your body is to tackle the day and take on a workout.
You’ll need seven days of data before you get your first score, with at least four hours of sleep in a session for that night to count. Once it’s unlocked, you’ll get a score from 1 to 10 (higher is better), categorized into four guidelines: Recover, Pace Yourself, Ready or Go for It. Unlike wearables that show you a recovery score in the morning, largely based on what happened overnight, Apple’s can change throughout the day as you drain or recharge your body.
In practice, though, I haven’t found it quite as dynamic or detailed as Garmin’s Body Battery, which shows a graph of how your energy changes throughout the day. I’ve noticed Apple’s Readiness score tends to update once or twice a day (depending on physical activity), with a one to two point drop near bedtime. I didn’t get any extra credit for a midday nap, for example; however, I noticed an immediate three-point drain after a 5-mile trail run on a hot day. Since there’s currently no way to see previous readiness scores or long-term trends, I’m left relying on memory to gauge the changes.
The Readiness score also seems to have a blind spot for women: the menstrual cycle. After tracking recovery across enough wearables, I’ve learned that one of the biggest factors in how I feel is where I am in my cycle, regardless of my score. Apple surfaces what day you’re on in your cycle right in the Readiness tab, but doesn’t explain how that stage affects your recovery.
Other wearables I’ve tested, like the Oura ring and Fitbit Air, go a step further. Around and after ovulation, for example, they’ll flag that workouts may feel harder or explain that a dip in HRV may be consistent with transitioning into the luteal phase. Whereas before I’d power through and chalk it up to a bad night of sleep, now I have a scientific explanation for why I feel wrecked the day after I ovulate and don’t schedule any big workouts.
There’s also a new Daytime toggle in the watch’s Vitals app that lets you see daytime heart rate and HRV alongside the overnight measurements, including temperature and blood oxygen.
10 additional hours of battery life
Battery life has always been one of the Ultra’s biggest advantages over the regular Apple Watch, generally buying you about an extra day between charges. This year, the Ultra 4 has a larger battery than the Ultra 3, and in my testing, it lasted 10 extra hours of normal use with the always-on display.
On my first full battery test, I got 60 hours on a charge, beating Apple’s 50-hour estimate by a significant margin. That included three 30-minute outdoor GPS workouts, and otherwise relatively light use, with fewer work notifications than I’d get on a typical busy day. In low power mode, which switches the display from always-on to raise-to-wake, you could feasibly stretch it to 84 hours, or about three and a half days, according to Apple. It also charges faster than its predecessors, getting up to 18 hours of use from just a 15-minute top-up with the included cable.
But the larger battery only accounts for half of the gain. The new S11 chip is also doing a lot of the heavy lifting in the battery department. It splits tasks between the main processor and a more power-efficient always-on processor that can handle background jobs, like the more frequent heart rate sampling, without constantly waking the main processor.
Finally, enough battery life for an ultramarathon
For endurance athletes, the Ultra 4 also has two workout-specific battery modes that let you trade certain features for significantly more tracking time. Extended Workout mode can stretch a continuous workout to 25 hours, up from a maximum of 20 hours on the Ultra 3, by dropping running-form metrics like vertical oscillation, cadence and stride while keeping GPS and heart-rate tracking at full fidelity.
Max Extended pushes that even further, to up to 45 hours, but makes bigger compromises. GPS drops from multiband to single-band, heart rate switches to a rolling five-minute average, and you lose things like splits, alerts and custom workouts. Once the workout ends, the watch goes back to your normal battery settings. The Series 12 also gets both of these workout modes.
I’m not one of those crazy ultramarathon people (yet), so I haven’t been able to test Apple’s claim, but I do know battery life has been a deal-breaker for people looking for multiday workout tracking. CNET Video Producer Dillon Lopez ditched his Ultra 2 after it failed to record his epic summit hike of Mount Whitney — it died on the descent.
Even with every power-saving mode activated, the Ultra 4 still won’t get anywhere near the weeks of battery life you can get from dedicated sports watches like some Garmin models. But these modes give you more control over what you’re willing to sacrifice to reach the finish line, while still keeping the seamless integration and other smartwatch features (like a now very capable Siri AI) that make the Apple Watch so convenient.
Your Apple Watch is listening, but not recording
The Ultra 4 and Series 12 also gain new Audio Intelligence features that help the watch make sense of the sounds around you, similar to how Siri can use the iPhone’s camera to understand what you’re looking at. The features available now include faster music recognition with Shazam and Sound Recognition, an accessibility feature that sends alerts for sounds like a crying baby, a siren or a doorbell. That last one has been hit or miss in my testing, with phantom alerts for sounds I couldn’t hear.
The more controversial features, and the ones that have made some Apple fans (myself included) uneasy, aren’t available yet and involve transcribing and summarizing live conversations. Live Rewind lets you double-click the Digital Crown to pull up a transcription of the previous 15 seconds of conversation, similar to how Live Photos on the camera let you see extra seconds before and after taking a shot. During my live demo at Apple Park, the transcription was spot-on despite the noisy environment and being a few feet away from the person recording.
Then there’s Siri Recap, which can listen in the background while enabled and generate high-level notes and summaries from meetings or other conversations you may want to revisit. You can trigger it manually, schedule it for certain times or places, or leave it enabled throughout the day. All of these features are opt-in, meaning they’re not enabled by default, but that hasn’t stopped people from worrying about their potential use cases.
Apple has built in significant privacy protections. Raw audio is processed inside a hardware-isolated compartment on the S11 chip and isn’t saved as an audio recording. Siri Recap condenses the transcript before sending anything to Private Cloud Compute, and Apple says the full transcript is then deleted, plus saved recaps don’t identify individual speakers.
But there’s another privacy question that those protections don’t address: the other people in the room. The part I’m still uneasy about is that there’s no obvious indicator light as you get on some of Meta’s smart glasses to signal that the watch is listening, and the people you’re talking to may have no idea you’ve enabled it.
Apple Watch Ultra 4: Bottom line
The 49mm screen and rugged build make the Ultra 4 too bulky for me to use as my everyday Apple Watch. But better battery life, more frequent health measurements and a new Readiness score make it a more tempting option for endurance athletes and anyone upgrading from an older Ultra. Just as importantly, none of those new health and recovery metrics are locked behind a subscription, a rare gem in a wearable market increasingly dominated by freemium features and subscription fees.
At $799, it’s still a splurge, but that price includes cellular and emergency satellite connectivity built into the watch. You’ll need a separate carrier plan to actually use cellular service, while Apple’s satellite service is included for the first two years.
The Ultra 4 still can’t match the weeks of battery life you can get from some dedicated sports watches from Garmin and Coros, but Apple seems to be making a different bet: that athletes will trade some of that longevity for highly accurate tracking, subscription-free health data on a smartwatch that can now make better use of that data throughout the day.
I don’t usually recommend upgrading from last year’s model (save money where you can), but this year may be the exception. The Readiness score and improved battery life make even an upgrade from the Ultra 3 compelling, especially for athletes who care about recovery metrics and need extra runtime during endurance workouts.
For everyone else, the Ultra 4 makes a stronger case that you don’t necessarily have to choose between a serious sports watch and an Apple Watch anymore.
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