Galaxy Watch Ultra vs Apple Watch Ultra 3: Which Battery Actually Lasts?

Engadget's headline on the Galaxy Watch Ultra 2 review calls it "the new standard for smartwatch battery life." That is a big claim for a category where the standard has long been "charge it tonight." Before anyone pays $650 or more for a bigger battery, it helps to know what the numbers mean and which phone sits in your pocket.

A note on method: this is a comparison built from manufacturer spec sheets and published reviews, not hands-on testing. I use the original Galaxy Watch Ultra's published figures, because they are the ones I can state with confidence. Check Samsung's listing for the Ultra 2's rated hours and treat Engadget's review as an independent test of them.

What the spec sheets promise

Samsung launched the original Galaxy Watch Ultra in July 2024 at $649.99. It has a 47mm titanium case, a 590 mAh battery, a 3,000-nit display and 10 ATM water resistance. Samsung rates it at up to 100 hours in power saving mode and around 60 hours in typical use.

Apple's Watch Ultra 3 launched in September 2025 at $799. Apple rates it at up to 42 hours of normal use and up to 72 hours in Low Power Mode. It is also a 49mm titanium watch with a 3,000-nit display, plus satellite connectivity and 5G cellular.

On paper, Samsung's rated hours run well ahead of Apple's. Garmin's Fenix 8 AMOLED (47mm, from $999.99) sits in another league, with Garmin rating up to 16 days in smartwatch mode. That figure assumes you are not running much GPS.

Rated hours are a lab number

Every one of these figures comes from the maker's own test conditions. Those usually involve a set number of notifications, a fixed block of workout time, and often an always-on display that behaves differently than yours does. Apple, Samsung and Garmin do not use the same recipe, so the headline hours are not directly comparable.

My read: treat the ratings as a ranking within one brand, not across brands. A watch that drops to 45 percent after one night of sleep tracking and a one-hour GPS run will not last 60 hours, whatever the box says. Sleep tracking is the most common battery hog in this category, which is the same problem I described in the smart ring review, only with a bigger battery to hide it.

The practical test is simple. If you wear the watch overnight, you need a battery that can absorb a night of tracking plus a full day and still have margin. Anything that needs a daily top-up is a watch you will eventually stop wearing to bed.

Who the Samsung is for

The Galaxy Watch Ultra is for Android users who want a rugged watch without paying Garmin prices. It is built to MIL-STD-810H durability standards and carries a dedicated orange Quick Button that you can map to a workout or flashlight. Samsung Health handles sleep, body composition and its sleep apnea feature.

The catch is the ecosystem. Samsung's watches are built for Android phones, and the best features lean on Samsung's own apps. Someone with a midrange Android phone like the Galaxy A37 can pair one, but a few features assume a recent Galaxy handset. An iPhone owner cannot use it at all.

Who the Apple is for

The Apple Watch Ultra 3 is for iPhone owners, full stop. It does not work with Android, so the comparison ends there for half the market. If you own an iPhone, it is the more polished product and has the better app library, but it costs $150 more at list price and gives you fewer hours between charges.

Its advantages are cellular and satellite features, the 86-decibel siren and a dive-ready rating that most buyers will never touch. Paying for those makes sense if you hike or swim in open water. For an office worker who wants step counts, it is expensive over-engineering.

Who should skip both

Skip both if you actually want multi-day endurance with heavy GPS use. Ultramarathoners, backpackers and anyone who records long activities every weekend are better served by Garmin, whose watches are designed around battery life first and apps second. The Fenix 8 costs more, but its rated hours are far beyond either of these.

Skip both if repairability matters to you. Neither watch has a user-replaceable battery, and a swollen cell two or three years in will mean a manufacturer service fee or a new watch. Compare that with the philosophy in our Fairphone 6 review, where the battery pops out in seconds. Wearables are still far from that standard.

Also skip them if a cheaper watch would do. A Galaxy Watch or Apple Watch SE-class model handles notifications, steps and heart rate for hundreds of dollars less. The Ultra tier is priced for durability and endurance, and you should only buy it if you will use both.

Bigger batteries, same arguments

This section is speculation. Battery capacity is one of the few areas where a wearable can improve without a new sensor or a new chip, so I expect Samsung and Apple to keep trading rated-hour claims each generation. If Engadget's verdict on the Ultra 2 holds up in other reviews, Apple will probably feel pressure to answer with a larger cell or more efficient silicon.

What I do not expect is a standardized test. Until the industry agrees on one, every "new standard" headline is a claim about the maker's own lab, not an independent benchmark. Independent runtime tests from reviewers are worth more than any spec sheet.

Verdict

For Android owners, the Galaxy Watch Ultra line is the most compelling big-battery smartwatch outside Garmin's catalog, and the Ultra 2 appears to push that lead further. For iPhone owners, the Apple Watch Ultra 3 is the only real choice, and its battery is acceptable rather than exceptional. Whichever you pick, buy based on the phone you own and the sleep tracking you will actually switch on. Rated hours on a box are the least reliable part of the sale.

Prices are manufacturer list prices at launch and may differ at retailers. Figures come from Samsung, Apple and Garmin spec pages and from Engadget's published headline; verify current specs for the Galaxy Watch Ultra 2 before buying.