For a runner, two lines on Apple’s spec sheets separate Apple Watch Ultra 4 from Apple Watch Series 12: workout battery and GPS. Series 12 is rated for up to 10 hours of outdoor workout with Precision L1 GPS, while Ultra 4 is rated for 18 hours, 25 hours in Extended Workout and 45 hours in the new Max Extended Workout mode, with precision dual-frequency GPS.
Everything that measures your body is the same on both: Apple’s tech specs give both watches the S11 chip and the new Health Sensing System, so heart rate sampling, the Readiness score and the Steps complication do not depend on which you buy. The $400 difference buys endurance, GPS and a tougher case.
Key facts for runners
| Spec | Apple Watch Series 12 | Apple Watch Ultra 4 |
|---|---|---|
| Outdoor workout battery | Up to 10 hours | Up to 18 hours |
| Extended Workout mode | Not listed | Up to 25 hours |
| Max Extended Workout mode | Not offered | Up to 45 hours, one-second GPS intervals |
| GPS | Precision L1 GPS (GPS, GLONASS, Galileo, QZSS, BeiDou) | Precision dual-frequency GPS (GPS, Galileo, QZSS, BeiDou) |
| Weight | 32.2 g (42 mm aluminum), 39.5 g (46 mm aluminum) | 63.0 g (Natural), 63.1 g (Black) |
| Peak brightness | 2000 nits | 3000 nits |
| Price | From $399, or $11.99 a month | From $799, or $24.99 a month |
Workout battery: 10 hours vs 18, 25 and 45
Apple rates Series 12 for up to 10 hours of outdoor workout, which its press release calls 25 percent more than before, inside an all-day rating of 24 hours. A 15-minute charge gives up to 12 hours of use and the watch reaches 80 percent in about 30 minutes. Details are in our Apple Watch Series 12 announcement coverage.
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Ultra 4 starts at 18 hours of outdoor workout and adds two longer modes. Extended Workout is rated for up to 25 hours, again 25 percent more than before, and Max Extended Workout for up to 45 hours while keeping one-second GPS intervals, which Apple says is aimed at 100-mile races. Normal use is 50 hours, a 15-minute charge gives 18 hours, and 80 percent takes about 45 minutes.
The practical line falls at the ultra distances. Ten hours covers a marathon for most runners with margin to spare; a 50-mile or 100-mile event, or a multi-day trek without reliable charging, is where Series 12 runs out of rated time and Ultra 4 does not.
GPS: L1 vs dual-frequency
Series 12 uses what Apple calls Precision L1 GPS, tracking GPS, GLONASS, Galileo, QZSS and BeiDou. Ultra 4 uses precision dual-frequency GPS across GPS, Galileo, QZSS and BeiDou, and Apple’s press release calls it the most accurate on-device GPS in a sports watch. Ultra 3’s specs listed the same dual-frequency L1 and L5 design, so this is a carry-over rather than a new radio.
Dual-frequency matters most where a single frequency struggles: dense city streets, tree cover and canyon trails. Apple has not published accuracy figures for either watch, so the difference rests on Apple’s claim, but the hardware gap is real and it is the second reason a trail runner leans Ultra.
What both watches share
| Feature | Series 12 | Ultra 4 |
|---|---|---|
| Chip | S11 | S11 |
| Heart rate sampling | Every 5 seconds | Every 5 seconds |
| HRV sampling | Every 5 minutes | Every 5 minutes |
| Readiness score (0 to 10) | Yes | Yes |
| Steps complication, step accuracy claim | Yes | Yes |
| Workout Buddy without iPhone | Yes, over Wi-Fi or cellular | Yes |
| Sleep score, hypertension notifications, ECG | Yes | Yes |
| 5G on cellular models | Yes | Yes |
The Readiness score is a daily 0 to 10 rating built from recent activity, training load, vitals and sleep, with four recommendations: Recover, Pace Yourself, Ready and Go For It. watchOS 27 also improves treadmill distance accuracy and adds pace, distance and duration insights to Workout Buddy on both models.
Weight, display, water and bands on the run
Ultra 4 is a 49 mm Grade 5 titanium case at 49 by 44 by 12 mm and 63 g, roughly double the 32.2 g of a 42 mm aluminum Series 12 and well above the 39.5 g 46 mm model. Its flat sapphire crystal peaks at 3000 nits against 2000 on Series 12, and it carries a 100 m water rating, MIL-STD 810H testing and an on-wrist temperature range of minus 20 to 55 degrees C. Aluminum Series 12 models get Ceramic Shield 2, which Apple calls 60 percent tougher than Ion-X, and a 50 m rating.
For trail runners, Ultra 4 also keeps Emergency SOS, Messages and Find My via satellite with two years included, as covered in our Ultra 4 announcement article. Series 12 has no satellite radio.
Bands split the same way: a Sport Band and Sport Loop in new colors for Series 12, and the Trail Loop, Alpine Loop and Ocean Band for Ultra 4.
What Apple has not said
- GPS accuracy in meters for either watch, or how the two compare on the same route.
- Whether the 10-hour Series 12 workout rating assumes GPS on, or how it changes with cellular in use.
- Whether Series 12 gets an Extended Workout mode through watchOS 27.
- Cellular pricing for either watch, and band prices.
- Any figures from the 1,000-person heart rate study beyond the claim that Apple Watch was the most accurate wearable tested.
Both watches are on pre-order now and reach stores on Friday, September 18: Series 12 from $399 and Ultra 4 from $799. Both need an iPhone 11 or later on iOS 27, which arrives on September 14. If your longest run is a marathon, Series 12 covers it; if you race through the night, the Ultra’s 25 and 45 hour modes are the reason to pay double.
