COMPARISON: Galaxy Watch8 vs Galaxy Watch Ultra 2025

For the year 2025, the Samsung It comes with the best options for smartphone users. Android And especially if you already own a smartphone from that brand. But which one to choose between the... Galaxy Watch8 and Galaxy Watch UltraSee the comparison in this post and choose the best one for your daily life.

Design

O Galaxy Watch8 Refines the ergonomics of the previous generation, featuring a 1,1 mm reduction in thickness. This change, while subtle on paper, translates into significantly greater comfort for daily use and during sleep. Available in the following finishes... Graphite e Silver, it maintains the minimalist aesthetic of the line.

In contrast, the Galaxy Watch Ultra (2025) It maintains the aggressive visual identity and the chassis in Titanium Unlike its predecessor, its 47mm "Squircle" design conveys robustness, but comes at a cost in ergonomics: the raised profile and extra weight can make it somewhat uncomfortable for thinner wrists or for sleep monitoring, where the excessive volume tends to bother users who move around a lot at night.

And it's worth highlighting that the Galaxy Watch Ultra It has an action button that allows you to activate a siren or start an action (such as beginning to monitor an exercise) with just one click. In everyday use, this is quite practical, especially since you need to start measuring exercises on the watch to have health data captured. The siren is also useful in emergencies, making it easy for first responders to find you.

We must also mention that the Galaxy Watch Ultra is superior in durability: it withstands temperatures up to 55°C and altitudes of 9.000m. 10 ATM water pressure, which is equivalent to a depth of approximately 100 meters and makes it suitable for swimming and snorkeling.

In contrast, the Galaxy Watch8 has water resistance of 5 ATM, equivalent to approximately 50 meters of sufficient depth, ideal for shallow swimming, but not for diving or high-speed water sports.

Fabric

Samsung equipped both models with panels. Super AMOLED protected by sapphire crystal, guaranteeing vibrant colors and high scratch resistance. Both also feature the Always On Display (AOD)which keeps the display visible with low power consumption. However, the implementation of this technology differs slightly between versions.

The Galaxy Watch8 focuses on maximizing usable screen space in a compact body. Available in 40mm (1.3 ″) e 44mm (1.5 ″)The great evolution of this generation lies in bezel reductionBy reducing the black bezel around the display, the Watch8 offers a more "infinite" and immersive visual experience.

This not only improves the aesthetics, making the watch more elegant for social use, but also facilitates interaction with the interface, offering more space for touches and gestures without increasing the physical size of the watch on the wrist. Despite this, because it lacks glass protection, the edges of the screen may scratch over time.

The Ultra model focuses on extreme functionality. Although its body is robust (47 mm), its screen is the same size as the larger version of the Watch8 (1.5"The key difference here isn't the size, but the power:

• 3.000 Nit Brightness: The panel achieves much higher peak brightness levels, ensuring perfect readability under direct midday sun, essential for outdoor sports.
• Exclusive Night Mode: The Ultra has a software feature integrated into the hardware that, upon detecting low light, automatically changes the settings. watch faces exclusive for one tactical monochromatic redThis preserves the user's night vision while camping or hiking, preventing pupil dilation caused by common white or bluish light.

The screen Galaxy Watch Ultra It wins. If you need to read notifications in bright sunlight or check GPS in the middle of the woods at night without dazzling your vision, the extra brightness and tactical Night Mode are tools that the standard model doesn't offer.

System and interface

Both smartwatches come with the WearOS 6via interface One UI 8 WatchAmong the new features for this year, I highlight the pill-shaped modules, which fit the screen better and, of course, allow for better viewing regardless of the angle from which you are viewing the watch. A tip that made a difference for me when using both devices: put the fonts in bold to see the information even better.

A Now Bar It's also here, albeit in a simple way. It allows you to control the music, view or pause timers, or even see real-time workout information, always at the bottom of the screen.

It's worth highlighting the good integration of the watches with smartphones from Samsung And how everything stays synchronized. One example is setting alarms; even if you only program an alarm on your smartphone, it will appear on your watches.

It's also worth mentioning the use of gestures for quick actions, such as shaking your wrist to turn off alarms and reject calls, a "tap tap" to open an app, and the pinch gesture, which can be used for various purposes. It's an addition that makes everyday life more dynamic.

Finally, the Wear OS 6 platform guarantees access to the vast library of Google Play Store, ensuring that essential apps like WhatsApp, Spotify, Strava, Google Maps, and more work natively and smoothly on both devices.

clock faces

Since both devices operate under the One UI Watch interface, they share a vast native library, from classic analog emojis to interactive AR emojis. However, Samsung has reserved crucial software differentiators for the more robust model.

O Galaxy Watch Ultra It stands out with exclusive dials, such as the Ultra AnalogSpecifically designed for "power users," these layouts take advantage of the 47mm case to display up to eight complications simultaneously—such as a compass, altimeter, and UV index—transforming the watch into a dense control panel, something that would tend to clutter the look of the Galaxy Watch8, since the standard model prioritizes elegance and minimalism.

The Ultra's biggest technical advantage, however, is the integration of "Automatic Night Mode." Unlike the Watch8, where night mode only reduces brightness, the Ultra's exclusive watch faces change the entire interface to a tactical red when low light is detected.

This feature goes beyond aesthetics: the wavelength of red light does not affect the rhodopsin, preserving the user's night vision during camping trips or activities in the early morning hours, a safety feature that the base model does not natively offer.

It's worth noting that, in terms of pure style, the Galaxy Watch8 user is not left wanting. The Wear OS platform allows access to applications such as Facer ou timeflik via Google Play Store, guaranteeing endless customization for both. The Watch8 focuses on aesthetic customization for everyday use, while the Ultra focuses on technical functionality for extreme environments.

Features

The two watches, despite some visual differences, share the same processor and BioActive sensor, making them neck and neck in several aspects. Let's go through each of their features:

Google Gemini

Os Galaxy Watch8 e WatchUltra They were the world's first smartwatches (although models with Wear OS 6 later adopted it as standard) to receive the Gemini as personal assistants, replacing the Google AssistantThe assistant Bixby, Samsung, it's still available here, but the button Home both watches activate the Gemini by default.

In everyday use, it's similar to what we've seen on smartphones, but with some differences. Samsung mentions that, in fact, the functionality is the Ask Gemini (Ask Gemini, in a free translation), so that he can respond or initiate some action on the clocks.

The functionality on both is exactly the same, and even if you don't have an eSIM to connect the smartwatches from... SamsungIt also "picks up" internet from the connected smartphone, which is interesting because you don't have to pick up your phone to talk to Google's personal assistant.

The idea is interesting, and if you have wireless headphones connected to your phone or watch, you can hear the response without having to take your phone out of your pocket, keeping it safe. Despite this, both models still have flaws, especially if you're in a noisy environment. In any case, the... Gemini It's still better than... Google Assistant And having it available on both smartwatches is a great addition.

Sleep quality

If your main goal is to understand how you sleep, then... Samsung It has democratized technology: both models deliver the same data package. However, the physical experience of sleeping with them is opposite. Both the Galaxy Watch8 as much as Ultra use the BioActive Sensor updated and AI algorithms to generate the Energy Score (Energy ScoreBoth monitor:

• Sleep Apnea Detection: Both are certified (FDA/Anvisa) to detect signs of moderate to severe sleep apnea, a vital preventive health resource.
• Sleep Stages: Wakefulness, REM, Light and Deep Sleep.
• Oxygenation (SpO2): Drops in oxygen saturation during the night.
• Skin Temperature: Used to refine the analysis of the menstrual cycle and overall health.

O UltraWith its slightly larger battery, it can last up to three nights of monitoring without needing to see the charger, offering peace of mind for those who are forgetful. watch8If you forget to charge it before bed and it's at 15%, it will likely "die" before you wake up, losing the night's data.

Despite the improvements in sensors, it's important to manage expectations: some "ghosts" from past generations still haunt both the Galaxy Watch8 and the Ultra. The software's accuracy isn't absolute and suffers from two historical inconsistencies in the Galaxy line.

The first point of attention is the nap detectionThe system promises to identify daytime naps to improve your... Energy ScoreHowever, accuracy fluctuates. In tests, the watches don't always "wake up" to record these brief moments of rest, ignoring data that could improve their daily recovery metrics. Errors occurred more frequently on the Watch8 than on the Watch Ultra, but the more robust model also failed in some measurements.

The second problem is the sleep continuityThere are scenarios where, upon briefly getting up (to go to the bathroom or get a drink of water) and returning to bed, the clocks prematurely end the sleep session. This directly impacts the final score, delivering a report that says you slept less than you actually did.

To compensate for these technical shortcomings, the Samsung shines in the interpretation of data with the Sleeping AnimalsAfter seven days of continuous use, the system analyzes your patterns—such as bedtime, consistency, and awake time—and assigns an "avatar" to your profile, ranging from best to worst:

• Lion
• Penguin
• Walrus
• Mole
• Porto Cervo
• Urchin
• Jacaré
• Shark

Sleep apnea

For those who like to monitor sleep data, the watches can also be used as sleep apnea detectors. Throughout all monitoring stages, the company emphasizes that the signals indicated by the watches should not be used as the sole diagnostic factors, but rather as a basis for a specialist to learn more about your sleep patterns.

You need to sleep with the watch on for two nights after activating the feature in the app. Samsung health (It is not activated natively) and, soon after you wake up, you will be able to check if there was any interruption in your breathing during the night.

There is no difference in sleep apnea measurement between the two devices, but it's worth remembering that you need to pay attention to the battery so that the watches don't run out of power during the night and the measurement isn't interrupted.

Monitoring of physical activities

Ever since I started testing Samsung smartwatches, the fitness tracking has always caught my attention. The most interesting thing about both "Galaxy Watches" in this comparison is that everything becomes more dynamic when you have a device like this.

A Samsung It also doesn't try to reinvent the wheel: some exercises are still detected automatically, such as Walking, Running, Cycling, Elliptical trainer, Rowing machine, Swimming in a pool e dynamic exercise (category that encompasses activities with high overall movement, such as most gym workouts).

In addition to automatic detection modes, the watches can track over 100 physical activities in real time, putting them on par in that respect. And that's where the similarities end.

O Galaxy Watch Ultra It differs from the Watch8 in its system of Dual frequency GPSwhich offers greater accuracy in locating a location in dense urban areas or on trails, surpassing the standard GPS of the Watch8.

O Action Button An additional feature, exclusive to the Ultra model, allows users to quickly start workouts or track laps during activity, something absent in the Watch8, which relies solely on the touchscreen and conventional side buttons.

In terms of durability, the WatchUltra has a superior water resistance, being certified for use in sea ​​water and recreational diving activities, while the watch8 It is best suited for swimming in a pool and general daily use.

Finally, the Personalized Running Coach of the Watch Ultra is more advanced and integrated with high-level performance metrics, providing deeper data for serious athletes compared to the more general insights offered by the Watch8.

Bioimpedance

Bioimpedance, or Bioelectrical Impedance Analysis (BIA), is a technology used in wearable devices to measure body composition. It works by sending low-intensity, imperceptible electrical currents through the body to assess tissue resistance.

Based on this resistance, the watch can estimate important health metrics, such as body fat percentage, skeletal muscle mass, and hydration levels. This measurement doesn't replace a real test with a professional and, of course, like all electronic devices, it can produce some errors, but it's worthwhile using this as a baseline. It's useful to have this information to track your progress over the days/months.

heart rate

Both Samsung galaxy watch8 as much as Samsung Galaxy Watch Ultra They use the same sensor technology for monitoring heart rate and advanced metrics. Both can detect:

• Optical Heart Rate (PPG) and ECG Sensor: Both watches offer continuous heart rate monitoring (PPG) and the ability to perform electrocardiograms (ECGs) to detect irregular rhythms, such as atrial fibrillation.
• Vascular Load: This metric measures the amount of stress on the vascular system using pulse wave analysis during sleep. High values ​​suggest arterial stiffness and are influenced by lifestyle factors such as salt and inactivity. Vascular Load is available on the Galaxy Watch8 series.
• Antioxidant Index: The Watch8 series introduced the first Antioxidant Index feature in a smartwatch. It measures carotenoid levels to provide insights into the antioxidant status of the diet, a useful metric for healthy aging.

Blood pressure meter

What also remains unchanged is blood pressure measurement. However, it is crucial to note that this functionality requires regular calibration (every four weeks) using a traditional (cuff) medical-grade blood pressure monitor. This additional calibration device can represent a significant extra cost for the user.

Since the Watch Ultra comes with a longer battery life and high blood pressure alerts that are useful at all times, the more expensive model ends up surpassing the traditional Watch8, but the performance of both models in terms of blood pressure measurement is the same.

Electrocardiogram

In terms of ECG capabilities, the two watches are also quite similar. In addition to the ability to perform an electrocardiogram (ECG) on demand to view the heart rhythm in real time, both models feature... Irregular Heart Rhythm Notification (IHRN)This feature proactively monitors heart rhythms in the background, identifying signs suggestive of atrial fibrillation (AF) and notifying the user to perform an ECG for further analysis.

It's important to remember that the ECG is always performed manually by the watch, so it's always necessary to follow the instructions to ensure good accuracy. The ECG results, including detailed graphs, are automatically synchronized with the Samsung Health Monitor app on your Galaxy smartphone.

This allows the user to track the evolution of their data throughout the day and over time, and it is possible to share this information with a doctor for review or consultation purposes, serving as support in a diagnostic process.

Stress

The watches measure stress by analyzing two types of data from the heart rate sensor: heart rate (HR) and heart rate variability (HRV), which is the difference in the intervals between heartbeats.

Although these measurements are approximations, they provide... insights Valuable insights into general stress trends and your body's physiological response. Accuracy improves as the watch collects more user data over time.

Users can choose between measuring stress manually or automatically. To ensure accurate results, it is recommended to keep the sensor clean, remain still during measurement, and ensure the wristband is properly fitted. High levels of chronic stress are associated with various health problems, making monitoring a useful tool for overall well-being.

AGEs Index

O AGEs Index (Advanced Glycation End Products) AGEs are a health indicator that assesses the accumulation of certain compounds in the body, which are associated with biological aging and the risk of chronic diseases. The accumulation of AGEs is natural, but accelerated by diets high in sugars and fats, as well as a sedentary lifestyle. The Galaxy Watch8 and Watch Ultra measure this index non-invasively to provide a relative assessment of overall metabolic health.

Monitoring AGEs (Advanced Glycation End Products) levels can help people lead healthier lives, as it allows them to identify how specific daily habits, such as diet and physical activity, directly impact biological age and oxidative stress.

When viewing the index in the Samsung Health app, the user is encouraged to make more conscious choices to keep levels low, which contributes to disease prevention and healthier aging.

Menstrual cycles

Through the skin temperature sensor that was introduced from the series Galaxy Watch5It is possible to track menstrual cycles. The tracking can be done through the Samsung Health app on your mobile phone, where the user enters the dates of their menstrual period.

This temperature sensor helps the algorithm estimate when ovulation may occur. Therefore, the hardware and tracking method are identical in both models, maintaining consistency of the feature across Samsung's latest watch lineup.

Card payments

For those who want to leave their cell phone at home, both watches also come with Samsung Wallet or Google Wallet, allowing you to register cards saved in your phone's apps on the smartwatches as well. This can be an interesting option for those who train more at night or simply want to disconnect from everything when exercising.

Since I own a Galaxy S25 Ultra, I was able to use my card from Nubankexcept in SamsungWalletNo problem, you just need to confirm in the bank's app for the card to be added to both watches.

I also tested Google Wallet, which works almost identically to Samsung Wallet, and without any payment errors. To make payments via the watch's NFC sensor, you need to set a swipe pattern or six-digit PIN, focusing on security.

Connectivity

NFC is present in both, but there are differences depending on who wants to have internet access at all times. This is because the Galaxy Watch8 only has versions with Bluetooth functionality, so if you need to be connected constantly, it's worth paying attention to that.

The Galaxy Watch Ultra has native eSIM support since its first generation, so there's no need to choose. At the same time, while the 40mm Galaxy Watch8 Bluetooth version costs around R$1.600, the Galaxy Watch Ultra 2025 is priced at around R$2.500; it's worth considering your daily needs to see if the additional cost will truly make a difference.

Samsung Health app

Available even for those who don't have a Samsung smartphone, this is the app to check all the data collected by the watches. The idea is to keep everything simplified so the user can not only view the data, but also share their health information.

The same app also comes pre-installed on the watches, allowing you to view your health data even without your phone, enabling independent use. If you're training outdoors or at the gym and prefer to leave your smartphone at home, you'll still have access to your health data, making it one of the most comprehensive health apps on the market.

In addition to viewing health data captured by the watches, you can also set reminders for medication, track your daily water intake (including indicating on the watch that you drank water via a shortcut), enter calories from what you ate during the day, and even input blood glucose data.

Samsung Health Monitor app

The Samsung Health Monitor is the hub of regulated medical resources (Software as a Medical Device – SaMD). But it exclusively requires you to have a Samsung smartphone to access the data. The watch can also capture ECG, blood pressure, and sleep apnea data, but viewing this on your smartphone will depend on whether you have a Samsung device.

This is where the Electrocardiogram (ECG) and Blood Pressure are located, and where sleep apnea detection is activated. Irregular Heart Rhythm Notification (IHRN)This last feature deserves special mention: it works silently in the background, analyzing your pulse while you are at rest and proactively alerting you to signs of Atrial Fibrillation, without you needing to open any menus.

For users who need to bring data to their office, the integration is flawless. The app converts ECG readings into... detailed PDF files, ready to be shared with your cardiologist via instant messaging.

Battery and charging

Battery life remains the "Achilles' heel" of the Galaxy line. Galaxy Watch8 (with a battery of up to 435 mAh in the larger model) delivers approximately 36h for use with the always-on display (AOD) turned off. However, Galaxy Watch Ultra, benefiting from a larger chassis and battery. 590 mAh, extends that mark to approximately 50h.

Although fast charging (0 to 100% in about an hour) helps mitigate the problem, comparison with competitors like Huawei — which achieve 7 days or more — is inevitable. However, it's necessary to understand the difference in architecture: while rivals use simplified systems (RTOS), Samsung runs the... Wear OS, a complex operating system that allows true multitasking and deep integration with Google apps, naturally consumes more energy.

Low battery life creates "charge anxiety." If you forget to plug in your watch before bed if it's low on battery, you risk it turning off during the night, resulting not in the loss of already synchronized data, but in irreversible gaps in your sleep monitoring history.

For those seeking uninterrupted 24/7 health tracking, establishing a near-daily charging routine is still mandatory in the Samsung ecosystem.

Price and availability

Available in Brazil since July 2025Both models are already available for purchase in Brazil at a price 30% lower than Samsung's suggested retail price. While writing this review, here are the options we found:

Clock	Mercado Livre	Amazon	Magazine Luiza
Galaxy Watch8 40mm	Bluetooth: R$1.619 Bluetooth + LTE: R$1.889	Bluetooth: R$1.619 Bluetooth + LTE: R$1.889	Bluetooth: R $ 2.161,39 Bluetooth + LTE: R$ R $ 2.599,00
Galaxy Watch8 44mm	Bluetooth: R$1.799,10 Bluetooth + LTE: R$2.069,10	Bluetooth: R$1.799 Bluetooth + LTE: R$2.299	Bluetooth: R $ 1.899,05 Bluetooth + LTE: R$ R$ 2.699,00
Galaxy Watch Classic 2025	R$2.499	R$2.599	R $ 2.659,05

Conclusion: which one should you buy?

The final decision comes down to your lifestyle. Galaxy Watch8 is, without a doubt, the more rational purchase For 90% of Brazilians, it delivers the same intelligence (Gemini), the same advanced health sensors, and an infinitely more comfortable design for sleeping and working, at a significantly lower cost. The loss in battery life and brightness is an acceptable compromise for the superior ergonomics.

Already Galaxy Watch Ultra It's a niche piece of equipment. It's only worth the investment if you fit into two profiles: outdoor athlete which requires 10 ATM water resistance and dual-frequency GPS for trails and sea, not to mention the emergency siren, which can be a good feature for potential emergencies.

Still, the more traditional Galaxy Watch8 delivers a more comfortable experience, with the same sensor found in the more robust model. The Galaxy Watch Ultra 2025 is far from a bad smartwatch, but keep in mind that you'll need to get used to having such a robust model on your wrist, which may even leave marks from overnight wear.

The battery is still a problem in both: Samsung It still needs to improve the battery life of its smartwatches, and although it's well-established in the smartwatch market, its operating system still demands a lot from the battery. Perhaps the next generation will bring us models with better battery life.

If you're willing to charge your watch daily in exchange for a smart, integrated ecosystem, the Watch8 is your ideal partner. If you need ruggedness and hate charging, the Ultra is your only option in the Galaxy line.

Technical Specifications

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With some info: VERSUS l GSM Arena

reviewed by Tiago Rodrigues in 08 / 12 / 2025