Short answer: the Garmin Fenix 8 lasts days to weeks between charges and is built around maps and long outdoor efforts; the Apple Watch Ultra 3 lasts about two days and is the better smartwatch for iPhone owners. Both have since been replaced: Apple sells the Apple Watch Ultra 4 (September 2026) and Garmin the fēnix 9 and fēnix 9 Pro (August 2026). This page compares the 2025 pair, then the 2026 pair, and says when the older one is still the better buy.
How this comparison is compiled. Figures come from Apple’s and Garmin’s own specification pages, owner’s manuals and press releases, checked in October 2026. Battery figures are the makers’ claims under their own conditions, and Apple and Garmin test differently. We have not tested these watches, and nothing here is a measured result.
Apple Watch Ultra 3 vs Garmin Fenix 8 at a glance
| Apple Watch Ultra 3 (2025) | Garmin Fenix 8 AMOLED, 47 mm (2024) | |
|---|---|---|
| US launch price | $799 | From $999.99 (series) |
| Works with | iPhone only | iPhone and Android |
| Battery, smartwatch use | Up to 42 hours | Up to 16 days (7 with always-on display) |
| Battery, GPS | Not published by Apple for this model | Up to 47 hours GPS only; 35 hours multi-band |
| Water and diving | 100 m; recreational scuba to 40 m | 10 ATM; dive-rated to 40 m |
| Maps | Offline maps via watchOS | Built-in routable topo maps |
| Apps and payments | Full App Store, Apple Pay, cellular | Garmin Connect IQ apps, Garmin Pay |
The 2026 models: Apple Watch Ultra 4 vs Garmin fēnix 9
| Apple Watch Ultra 4 | Garmin fēnix 9 | Garmin fēnix 9 Pro | |
|---|---|---|---|
| Announced | 9 September 2026 | 25 August 2026 | 25 August 2026 |
| US price | From $799 | From $999.99 | From $1,099.99 |
| Sizes | 49 mm | 43, 47, 51 mm | 43, 47, 51 mm |
| Battery, smartwatch use | Up to 50 hours; 84 in Low Power Mode | Up to 29 days (largest size) | Up to 31 days (largest AMOLED); up to 57 days on solar models with 3 hours a day outdoors |
| Battery, workout | Up to 18 hours workout tracking | Not published in the release | Not published in the release |
| Display brightness | Up to 3,000 nits | AMOLED, “twice as bright” as Fenix 8 | Up to 3,000 nits |
| GPS | Dual-frequency | Multi-band | Multi-band |
| Cellular / satellite | 5G and LTE, plus satellite | No | LTE and satellite (plan required) |
| Diving | Recreational scuba to 40 m | Dive-rated to 40 m | Dive-rated to 40 m |
| Storage | 64 GB | 64 GB, up to 7,000 songs | 64 GB |
| Works with | iPhone 11 or later | iPhone and Android | iPhone and Android |
Garmin’s fēnix 9 Pro is the first fēnix with a titanium case and adds an LED flashlight; the 51 mm Pro has a 1.5-inch display, 15% larger than the Fenix 8’s without a larger case. Garmin’s release does not list GPS-hour figures or weights; check the owner’s manual before relying on a workout-battery comparison.
Check Apple Watch Ultra 4 prices on Amazon · Check Garmin fēnix 9 prices on Amazon
Which is better for you?
- Multi-day hikes, ultras, expeditions: Garmin. Even the older Fenix 8 47 mm lists 47 hours of GPS, and the fēnix 9 lists up to 29 days of smartwatch use; the Ultra 4 lists 18 hours of workout tracking.
- Navigation: Garmin, with built-in routable maps; Garmin says the fēnix 9 pans maps up to 30% faster than the Fenix 8.
- iPhone owner who wants one watch for everything: Apple Watch Ultra 4, for apps, Apple Pay, calls and cellular.
- Android phone: Garmin; no Apple Watch works with Android.
- Calls and SOS without a phone: Ultra 4 (cellular and satellite) or fēnix 9 Pro (LTE and satellite with a plan).
- Budget: the Ultra 4 starts $200 below the fēnix 9. A discounted Fenix 8 or Ultra 3 can be cheaper still.
Should you still buy the Fenix 8 or Ultra 3?
At a real discount, yes. The Fenix 8 still lists longer GPS battery (47 hours) than the Ultra 4 lists for workouts (18 hours), and has the same 40 m dive rating as the fēnix 9. The Ultra 3 costs the same $799 at list as the Ultra 4, so it only makes sense well below that.
Frequently asked questions
Garmin Fenix 8 vs Apple Watch Ultra 3: which has better battery life?
The Fenix 8: Garmin lists up to 16 days of smartwatch use for the 47 mm AMOLED model, against Apple’s 42 hours for the Ultra 3.
Does the Garmin Fenix work with iPhone?
Yes. Garmin watches pair with both iPhone and Android phones through Garmin Connect.
Is the fēnix 9 worth upgrading to from the Fenix 8?
Garmin’s listed gains are a brighter display, faster maps with twice the map storage, and longer smartwatch battery (up to 29 days on the largest size). LTE and satellite need the fēnix 9 Pro. If those do not matter to you, the Fenix 8 remains a capable watch.
Sources
- Garmin, fēnix 9 and fēnix 9 Pro press release, 25 August 2026: garmin.com newsroom
- Garmin, fēnix 8 AMOLED owner’s manual (battery table)
- Apple, Apple Watch Ultra 4 and Ultra 3 specifications: apple.com
Checked 17 October 2026.
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