Comparison · Fitness watches · Desk research
Apple Watch SE 3 vs Apple Watch Ultra 4
Quick Answer
Apple Watch SE 3 (year introduced 2025, Support 125094) is a 40mm or 44mm aluminum watch with the S10 SiP, a 4-core Neural Engine, 64GB, Always-On Retina OLED with LTPO, Ion-X glass, up to 1,000 nits (2 nits minimum), 324×394 / 368×448 at 326 ppi, L1 GPS, 50m swimproof, a temperature sensor, Crash Detection, and Fall Detection. Apple lists up to 18 hours of normal use, 32 hours in Low Power Mode, about 80% in 45 minutes, and 15 minutes.
The verdict
Apple Watch SE 3 or Apple Watch Ultra 4 — quote the two manufacturer sheets.
Why: SE 3 is the current-sold 40/44mm aluminum value Watch: S10, 64GB, Always-On LTPO OLED at 1,000 nits, temperature sensor, L1 GPS, 50m, Crash/Fall Detection, and Apple’s 18-hour / 32-hour Low Power table. Apple’s compare table and ECG footnote exclude SE models. Ultra 4 is the 49mm Grade 5 titanium adventure SKU on S11 with dual-frequency GPS, satellite, Action Button, 100m / 40m dive, Health Sensing System, and the 50 / 84 / 45-hour table. Both are named on Apple’s watchOS 27 list.
Buy Apple Watch SE 3 if
You want a current Apple Watch that is still on watchOS 27, Always-On, and Crash/Fall Detection in a 40mm or 44mm aluminum case, and you do not need ECG, dual-frequency GPS, satellite, or Ultra’s multi-day battery table.
Buy Apple Watch Ultra 4 if
You want Apple’s current 49mm adventure watch: Grade 5 titanium, Action Button, dual-frequency GPS, satellite SOS/Messages/Find My, ECG, Health Sensing System, and Apple’s 50-hour normal-use / 45-hour Max Extended Workout claims.
Spec comparison
OEM rows only. SE 3 numbers are from Apple Support 125094. Ultra 4 numbers are from apple.com/apple-watch-ultra-4/specs/. Cells Apple does not publish stay marked.
| Spec | SE 3 | Ultra 4 |
|---|---|---|
| Year introduced | 2025 (Support) | 2026 (Newsroom 9 September 2026) |
| Case size(s) | 40mm and 44mm | 49mm only |
| Case material | Aluminum (Starlight, Midnight) | Grade 5 titanium |
| Dimensions (44mm / 49mm) | 44 × 38 × 10.7mm | 49 × 44 × 12mm |
| Display | Always-On OLED + LTPO; 40mm 324×394; 44mm 368×448; 326 ppi; up to 1,000 nits; 2 nits minimum | Always-On LTPO3; 422×514; 326 ppi; 3,000 nits peak; 1 nit minimum |
| Front crystal | Ion-X (Apple: 4x crack resistance footnote) | Flat sapphire |
| Chip / storage | S10; 64-bit dual-core; 4-core Neural Engine; 64GB | S11; 64GB |
| Battery — normal use | Up to 18 hours (July–August 2025 tests) | Up to 50 hours |
| Battery — Low Power / extra modes | Up to 32 hours Low Power | Up to 84 hours Low Power; 18 hours outdoor; 25 hours Extended; 45 hours Max Extended Workout |
| Fast charge (OEM) | ~80% in about 45 minutes; 15 min ≈ 8 hours | ~80% in about 45 minutes; 15 min ≈ 18 hours |
| Weight (example SKUs) | GPS 44mm 32.9g; GPS+Cellular 44mm 33.0g; GPS 40mm 26.3g | 63.0g natural titanium; 63.1g black titanium (case only) |
| GNSS | L1 GPS (GLONASS, Galileo, QZSS, BeiDou) | Precision dual-frequency GPS |
| Water | 50m (ISO 22810:2010); Apple: not scuba or high-velocity water | 100m (ISO 22810:2010); EN 13319 recreational dive to 40m |
| Dust | Not listed on Support 125094 | IP6X; MIL-STD-810H subsection list |
| Action Button / siren | Not listed | Action Button; siren Apple says is audible to 180m / 600 feet |
| Satellite | Not listed | Emergency SOS, Messages, Find My via satellite |
| Heart rate | Second-generation optical heart sensor | Health Sensing System |
| ECG | Not applicable (Apple compare + ECG footnote excludes SE) | ECG app (Series 4+, excluding SE) |
| Blood Oxygen | Not listed on Support 125094 | Blood Oxygen app (region limits) |
| Temperature | Temperature sensor listed | Temperature sensor (Apple: Series 8 or later, SE 3, Ultra models) |
| Safety | Emergency SOS, Crash Detection, Fall Detection | Same class plus satellite radios, siren, flashlight |
| OS / phone | Support lists iPhone 11 or later / SE 2+ with iOS 26 or later | watchOS 27; iPhone 11 or later / SE 2+, iOS 27 |
| watchOS 27 (Apple list) | Named (SE 3) | On the list (Ultra 2 or later) |
| US start (dated) | Still sold; date apple.com — not invented here | $799 (Newsroom, 9 September 2026) |
Who each watch is for
SE 3 is Apple’s still-sold value Watch that is actually on the watchOS 27 list. Always-On and a temperature sensor are on Support 125094. ECG is not. If 40/44mm aluminum, L1 GPS, and an 18-hour table are enough, this is the current SE URL — not SE 2.
Ultra 4 is the current adventure Apple Watch. The comparison is case class, ECG / Health Sensing System, dual-frequency GNSS, satellite, dive path, and Apple’s 50 / 84 / 45-hour table.
watchOS 27 — quote Apple
Series 12 Newsroom, 9 September 2026: “watchOS 27 will be available for Apple Watch Series 9 or later, Apple Watch SE 3, and Apple Watch Ultra 2 or later … and requires iPhone 11 or later or iPhone SE (2nd generation or later) with iOS 27 or later.” SE 3 is on that sentence. SE (2nd generation) is not.
ECG and Blood Oxygen
Apple’s SE 3 compare page marks ECG as not applicable. The footnote excludes Apple Watch SE models. Support 125094 does not list a Blood Oxygen app. Ultra 4 lists ECG, Blood Oxygen, and the Health Sensing System. Do not write ECG onto SE 3.
Battery
Copy Apple’s mode names. SE 3: 18h / 32h Low Power; 15 minutes → up to 8 hours (July–August 2025 tests). Ultra 4: 50 / 84 / 18 / 25 / 45 hours; 15 minutes → up to 18 hours. Max Extended Workout is outdoor run/walk/hike with GPS every second.
GNSS, water, and satellite
SE 3 is L1 GNSS and 50m swimproof. Ultra 4 is dual-frequency GNSS, 100m / 40m dive, Action Button, and satellite. Do not upgrade SE 3 to “Ultra GPS” in prose.
Price
$799 is Apple’s published US starting price for Ultra 4 on 9 September 2026. This page does not invent an SE 3 start price. Date apple.com/apple-watch-se-3/.
Frequently asked questions
Does Apple Watch SE 3 get watchOS 27?
Yes, as named. Apple’s Series 12 Newsroom (9 September 2026) says watchOS 27 will be available for Apple Watch Series 9 or later, Apple Watch SE 3, and Apple Watch Ultra 2 or later, and requires iPhone 11 or later or iPhone SE (2nd generation or later) with iOS 27 or later. SE (2nd generation) is not on that list.
Does SE 3 have ECG?
Apple’s SE 3 / Series 12 compare page marks ECG as not applicable on SE 3. The ECG footnote on that page: the ECG app is available on Series 4 and later (excluding Apple Watch SE models) and all Ultra models. Do not write ECG onto SE 3.
Does SE 3 have Always-On and a temperature sensor?
Yes on Support 125094: Always-On Retina display with OLED and LTPO, and a temperature sensor. SE (2nd generation) Support does not list Always-On or temperature sensing — that contrast lives on /watches/apple-watch-se-2-vs-apple-watch-ultra-4/.
What are the SE 3 battery claims?
Support 125094: up to 18 hours of normal use; up to 32 hours in Low Power Mode; up to 80% charge in about 45 minutes; 15 minutes for up to 8 hours of normal use; 8 minutes for up to 8 hours of sleep tracking (July–August 2025 tests). Ultra 4: 50 / 84 / 18 / 25 / 45 hours; 15 minutes ≈ 18 hours.