Apple Watch Ultra 4 Earns Upgrade Status With Readiness Score, Longer Battery Life and No Subscription

Turn the Apple Watch Ultra 4 over and the difference shows up on the back. The Ultra 3 had a dual ring of sensors. The new model has 32 electrodes arranged like the petals of a gerbera daisy, which gives them more surface area for ECG readings. The green and infrared LEDs now sit in a smaller circular cluster at the center. CNET's reviewer, who has worn the $799 watch for a week and is still running battery tests, says those hardware changes are the start of a case for upgrading, something she rarely recommends.

The redesigned sensors work together with the new S11 processor. Together they let the watch take a heart-rate reading every 5 seconds, where earlier models managed roughly one every 5 minutes. Heart-rate variability, or HRV, is now sampled every 5 minutes instead of a few times a day. That denser data feeds a new Readiness score, Apple's estimate of how prepared your body is for the day and for a workout. It requires no subscription.

The score needs seven days of data before the first one appears, and a sleep session must last at least four hours to count. After that, the watch gives a number from 1 to 10, higher being better, sorted into four labels: Recover, Pace Yourself, Ready or Go for It. Unlike wearables that set a recovery score in the morning from overnight data, Apple's can move during the day. The reviewer found it less dynamic than Garmin's Body Battery, which graphs energy through the day. Her Readiness score updated once or twice daily and usually dropped a point or two near bedtime. A midday nap earned nothing, but a 5-mile trail run on a hot day cost her three points at once. There is currently no way to see past scores or long-term trends, so she relies on memory.

She also flags a gap around the menstrual cycle. The Readiness tab shows which day of the cycle you are on but does not explain how that stage affects recovery. The Oura ring and Fitbit Air go further, she says, noting that workouts may feel harder after ovulation or that an HRV dip may fit the transition into the luteal phase. A new Daytime toggle in the Vitals app shows daytime heart rate and HRV next to overnight measurements, including temperature and blood oxygen.

Battery life is where the gains are clearest. The Ultra 4 has a larger battery than the Ultra 3, and the reviewer got 10 extra hours of normal use with the always-on display. Her first full test ran 60 hours, against Apple's 50-hour estimate. It included three 30-minute outdoor GPS workouts and lighter-than-usual notifications. In low power mode, which swaps the always-on display for raise-to-wake, Apple says it can stretch to 84 hours. Charging is faster too: a 15-minute top-up with the included cable gives up to 18 hours. The S11 helps by handing background tasks, such as the frequent heart-rate sampling, to an efficient always-on processor, so the main chip stays asleep.

Two workout-specific modes target endurance athletes. Extended Workout stretches a continuous workout to 25 hours, up from 20 on the Ultra 3, by dropping running-form metrics like vertical oscillation, cadence and stride while keeping GPS and heart rate at full fidelity. Max Extended reaches up to 45 hours with bigger trade-offs: GPS falls from multiband to single-band, heart rate becomes a rolling five-minute average, and splits, alerts and custom workouts disappear. The Series 12 gets both modes. The reviewer has not tested the claims, but notes that CNET video producer Dillon Lopez dropped his Ultra 2 after it died on the descent of Mount Whitney. Even so, the Ultra 4 will not match the weeks of battery life of some Garmin and Coros sports watches.

New Audio Intelligence features, shared with the Series 12, are more contentious. Faster Shazam music recognition and Sound Recognition, which alerts you to things like a crying baby, a siren or a doorbell, are available now. The reviewer found the doorbell alerts hit or miss, with phantom notifications. Live Rewind, which transcribes the previous 15 seconds of conversation with a double-click of the Digital Crown, and Siri Recap, which can summarize meetings or conversations in the background, are not out yet. In a demo at Apple Park, Live Rewind was accurate despite noise. All of it is opt-in. Apple says raw audio is processed in a hardware-isolated compartment on the S11 and is not saved, and that Siri Recap condenses the transcript before sending it to Private Cloud Compute and then deletes the full transcript. Saved recaps do not identify speakers. The reviewer's unease is about bystanders: there is no indicator light, as on some Meta smart glasses, so people nearby may not know the watch is listening.

Her verdict is that the 49mm case is too bulky for her daily wear, but the Ultra 4 suits endurance athletes and owners of older Ultras. The $799 price includes cellular hardware and emergency satellite connectivity, though a separate carrier plan is needed for cellular, and satellite service is free for two years. She says even Ultra 3 owners who care about recovery data and runtime have a reason to upgrade. The privacy questions around Live Rewind and Siri Recap will be the thing to watch once they arrive.