Five years separate Apple Watch Series 7 from Series 12, and in that time Apple has changed the chip four times, doubled peak brightness from 1000 to 2000 nits, moved from 41 mm and 45 mm cases to 42 mm and 46 mm, added temperature, depth and water temperature sensors, and raised the battery rating from 18 hours to 24. The starting price has not moved: Apple’s press release for Series 7 said $399 in October 2021, and Series 12 starts at $399 today.
The other change is software. Apple’s watchOS 27 compatibility list begins at Series 9, so Series 7 stays on watchOS 26, while Series 12 ships with the new release described in our Series 12 announcement coverage.
| Key fact | Series 12 (Apple’s tech specs) |
|---|---|
| Price | From $399; $11.99 a month on a 24-month Apple Upgrade lease |
| Chip | S11, 64-bit dual-core, 4-core Neural Engine, 64GB storage |
| Display | 2000 nits peak, 1 nit minimum, 326 ppi |
| Sensors | New optical and electrical heart sensors, temperature, depth gauge to 6 m, water temperature |
| Battery | Up to 24 hours; 38 hours Low Power Mode; 10 hours outdoor workout |
| Charging | 80 percent in about 30 minutes; 15 minutes gives up to 12 hours |
| In stores | Friday, September 18 |
Series 12 vs Series 7: every spec side by side
| Spec (Apple’s tech specs and Apple Support) | Series 12 (2026) | Series 7 (2021) |
|---|---|---|
| Chip | S11, 4-core Neural Engine | S7, 64-bit dual-core, with W3 and U1 chips |
| Case sizes | 42 mm, 46 mm (ceramic 43 mm, 47 mm) | 41 mm, 45 mm |
| Materials | Aluminum, titanium, ceramic | Aluminum, stainless steel, titanium |
| Peak brightness | 2000 nits, 1 nit minimum | 1000 nits |
| ECG and Blood Oxygen | Yes | Yes |
| Temperature sensor | Yes | No |
| Depth gauge, water temperature | Yes, to 6 m | No |
| Heart rate frequency | Every 5 seconds; HRV every 5 minutes | Not published |
| Water resistance | 50 m, IP6X | 50 m |
| Battery | Up to 24 hours | Up to 18 hours |
| Low Power Mode | Up to 38 hours | Available; hours not stated by Apple |
| 80 percent charge | About 30 minutes | About 45 minutes (Apple’s compare page) |
| watchOS 27 | Yes | No (last major release watchOS 26) |
| Launch price | $399 | $399 |
Chips: S7 to S11 in four steps
Apple Support lists the Series 7’s S7 as a 64-bit dual-core processor paired with W3 wireless and U1 Ultra Wideband chips. Series 8 moved to the S8, Series 9 to the S9 with a 4-core Neural Engine, Series 10 and 11 to the S10, and Series 12 to the S11, which Apple calls its most powerful wearable chip. Series 12’s tech specs list a 64-bit dual-core processor, a 4-core Neural Engine, 64GB of storage and a second-generation Ultra Wideband chip.
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The S11 also has a Secure Exclave, a hardware-isolated compartment for on-device audio processing with immediate deletion. It powers Audio Intelligence: Sound Recognition alerts for sirens, alarms, doorbells and baby cries, Live Rewind for the previous 15 seconds of conversation as text, Siri Recap and Shazam. Apple’s Series 12 page says Sound Recognition arrives late 2026.
Sensors: three additions and a new heart rate stack
Series 7 had ECG and Blood Oxygen, and Apple Support lists no temperature sensor, depth gauge or water temperature sensor. Series 12 has all three, plus new optical and electrical heart sensors with larger green LEDs. Apple’s press release says they read heart rate every five seconds all day and HRV every five minutes, split into Recovery HRV and overall HRV, and that a study of more than 1,000 participants found the most accurate heart rate sensing in a wearable.
Those readings feed the Readiness app, a daily 0 to 10 score with four recommendations: Recover, Pace Yourself, Ready and Go For It. Apple also claims the most accurate step tracking of any smartwatch and adds a Steps complication.
Display, battery and charging
Series 7 peaked at 1000 nits. Series 12 peaks at 2000 nits, dims to 1 nit and uses LTPO3 wide-angle OLEDs that refresh down to 1 Hz for Always-On, according to Apple’s tech specs. Aluminum models get Ceramic Shield 2, which Apple says is 60 percent tougher than Ion-X glass.
Battery ratings move from up to 18 hours on Series 7 to up to 24 hours on Series 12, with 38 hours in Low Power Mode and 10 hours of outdoor workout. Charging to 80 percent drops from about 45 minutes, per Apple’s compare page for Series 7, to about 30 minutes, and Series 12 gets up to 12 hours from a 15-minute charge.
Software: Series 7 stops at watchOS 26
Apple’s watchOS page lists SE 3, Series 9 and later, and Ultra 2 and later for watchOS 27, with an iPhone 11 or later on iOS 27. Series 7 therefore misses Siri AI in beta, the dynamic app grid, the Smart Stack tap gesture, Workout Buddy without an iPhone nearby and the perimenopause features in Cycle Tracking. Apple has not said how long watchOS 26 will keep receiving security updates.
What Apple has not said
- Titanium, ceramic, cellular and band prices for Series 12.
- A trade-in value for Series 7; Apple’s Trade In page shows no per-model estimate without condition questions.
- Low Power Mode hours for Series 7, and its heart rate sampling frequency.
- How long Series 7 will stay on supported watchOS 26 releases.
Series 12 is on pre-order now from $399 and reaches stores on Friday, September 18, according to Apple’s press release. Series 7 owners who want a cheaper path to watchOS 27 can look at the $249 Apple Watch SE 3, though it lacks ECG and Blood Oxygen, or step up to the $799 Apple Watch Ultra 4.
