OnePlus Watch 3 43mm VS Xiaomi Watch S4 41mm

Both watches share the same 1.32″ OLED/AMOLED screen with an identical 466 × 466 px resolution, Always-On Display support, a 5 ATM water resistance rating, and a replaceable band — so on the surface they look like near-identical propositions. The meaningful differences, however, emerge the moment you look at physical dimensions and build choices.

The Xiaomi Watch S4 41mm is the more compact and wearable of the two: at 9.5 mm thick versus 11 mm, and 32 g versus 37.8 g, it is noticeably slimmer and nearly 6 grams lighter. That gap translates directly to all-day comfort, especially during sleep tracking or workouts. Its smaller 41.2 × 41.2 mm footprint (versus 43.2 × 43.2 mm) also makes it a better fit for smaller wrists. Critically, the Xiaomi adds sapphire glass — one of the hardest transparent materials used in watchmaking — giving it substantially better scratch resistance over the OnePlus Watch 3, which lacks any branded damage-resistant glass.

The OnePlus Watch 3 counters with a slightly higher pixel density of 352 ppi compared to 320 ppi on the Xiaomi, which can mean marginally crisper text and fine detail on-screen, though both are sharp enough for practical use. Overall, the Xiaomi Watch S4 holds a clear design edge: it is slimmer, lighter, physically smaller, and better protected against scratches — advantages that matter more day-to-day than the OnePlus's modest pixel density lead.

The sensor foundation shared by both watches is solid: heart rate monitoring, SpO2 tracking, GPS, accelerometer, gyroscope, and compass are all present on both the OnePlus Watch 3 and the Xiaomi Watch S4. For the majority of fitness and health tracking use cases — running, cycling, sleep, step counting, or swim tracking — neither watch leaves you underequipped.

Where the Xiaomi Watch S4 pulls ahead is in two specific additions: a temperature sensor and a barometer. The temperature sensor enables body or ambient temperature readings, useful for wellness monitoring and detecting early signs of fever or physiological stress. The barometer is arguably the more practically impactful of the two — it measures atmospheric pressure to deliver accurate altitude tracking and floor-climb counting, and it also improves GPS elevation accuracy during hikes or trail runs. The OnePlus Watch 3 carries neither, which is a meaningful gap for outdoor enthusiasts or users who want richer health data.

On sensor coverage, the Xiaomi Watch S4 holds a clear advantage. The barometer and temperature sensor are not niche additions — they contribute to more accurate activity tracking and broader health insight. Users who stay primarily on flat terrain or focus on basic fitness metrics will rarely notice the difference, but for anyone into hiking, altitude sports, or detailed wellness monitoring, the Xiaomi's sensor suite is the more capable of the two.

Activity tracking is one area where the OnePlus Watch 3 and Xiaomi Watch S4 are in complete lockstep. Every capability in this group — sleep tracking with reports, step and distance counting, pace measurement, automatic activity detection, route tracking, elevation tracking, exercise tagging, and calorie intake logging — is present on both watches without exception.

The breadth of shared features is genuinely impressive for both devices. Automatic activity detection removes the friction of manually starting a workout, route tracking paired with elevation logging covers the needs of most outdoor athletes, and calorie intake tracking pushes these watches toward a more holistic health management role rather than pure fitness recording. Neither watch is designed for diving, but that is a highly specialized use case unlikely to affect the vast majority of buyers.

This group is a complete tie. Based strictly on the provided specs, there is no differentiator to speak of — both watches deliver an identical activity tracking feature set. Choosing between them on this dimension alone is impossible, and prospective buyers should weigh other spec groups to make their decision.

Connectivity is where the gap between these two watches widens considerably. The Xiaomi Watch S4 carries a cellular module, meaning it can make calls, receive notifications, and stream data independently of a paired smartphone — a fundamental freedom the OnePlus Watch 3 simply cannot offer. Add to that iOS and Android compatibility on the Xiaomi versus Android-only on the OnePlus, and the S4 immediately serves a much broader audience.

On the finer points, the Xiaomi also runs Bluetooth 5.4 against the OnePlus's Bluetooth 5.2. While both are modern and reliable, 5.4 brings incremental improvements in connection stability and energy efficiency. Both watches support NFC for contactless payments and Galileo satellite navigation alongside other GNSS systems, and neither supports Wi-Fi or ANT+ — so those are non-factors in differentiating the two.

The Xiaomi Watch S4 wins this category decisively. Cellular connectivity is a premium feature that redefines how independently a smartwatch can operate, and cross-platform compatibility makes it viable for a far wider user base. iPhone users are outright excluded from the OnePlus Watch 3, which is a hard constraint — not a trade-off.

The battery story here is one of the most striking contrasts in this entire comparison. The OnePlus Watch 3 packs a larger 354 mAh cell versus the Xiaomi Watch S4's 320 mAh, yet the Xiaomi delivers a claimed 8 days of battery life against just 2.5 days on the OnePlus. That is a more than threefold difference in endurance from a smaller battery — a result that points squarely to the OnePlus consuming significantly more power, likely driven by its more demanding processing or display configuration.

In practical terms, 2.5 days means the OnePlus Watch 3 needs charging every other day without fail — a routine that many users find disruptive, particularly for uninterrupted sleep tracking. The Xiaomi's 8-day stamina, by contrast, comfortably covers a full week plus buffer, reducing charging anxiety to a once-a-week ritual. The Xiaomi further extends its convenience advantage with wireless charging support, which the OnePlus lacks entirely — a small but appreciated quality-of-life feature that removes the need to carry a proprietary cable.

On battery, the Xiaomi Watch S4 wins by a wide margin. Longer endurance and wireless charging together make it the more practical choice for users who prioritize low-maintenance daily wear, and the fact that it achieves this with a smaller battery only underscores the efficiency gap.

Across the broad feature set, these two watches are remarkably well-matched. Health tools like HRV tracking, VO2 max measurement, readiness scoring, and resting heart rate monitoring are present on both, as are everyday smartwatch staples — call answering, notifications, voice commands, vibrating alerts, stopwatch, and a generous 32GB of internal storage. Neither watch offers ECG, irregular heart rate warnings, or a smart alarm, so those absences are shared equally.

Two features tip the balance toward the Xiaomi Watch S4. First, fall detection — absent on the OnePlus Watch 3 — is a meaningful safety net, particularly for older users or those engaging in high-intensity outdoor activities. It can automatically trigger an alert if a hard fall is detected and the wearer is unresponsive, a capability that goes beyond fitness tracking into genuine personal safety. Second, the Xiaomi is listed as acquiring GPS faster, which in practice means less standing-around time waiting for a signal lock before a run or ride — a small but real convenience for anyone who trains regularly.

The Xiaomi Watch S4 edges ahead in this category. The feature parity is high, but fall detection is not a trivial addition — it adds a layer of safety utility that the OnePlus Watch 3 simply does not provide, and faster GPS acquisition further refines the day-to-day experience for active users.

When it comes to app and software features, the OnePlus Watch 3 and Xiaomi Watch S4 are mirror images of each other. Both platforms deliver activity reports, calorie burn tracking, inactivity alerts, goal setting, and achievements — covering the core loop of setting targets, monitoring progress, and staying motivated. Wellness-oriented additions like water intake tracking and weight tracking round out an identical feature set on both sides.

The one shared absence worth noting is a barcode scanner in the companion app, which some fitness platforms use to simplify food logging. Neither watch offers it, so calorie and nutrition tracking relies on manual input for both — a limitation that applies equally and does not favor either product.

This group is a complete tie. Every app and software feature listed is present on both watches without exception, and neither holds any advantage over the other. Users should look to other specification groups to differentiate between the two.

The miscellaneous spec group offers no grounds for differentiation whatsoever. Both the OnePlus Watch 3 and the Xiaomi Watch S4 share an identical profile here: a battery level indicator is present on both, while Windows and Mac OS X compatibility, an external memory slot, and a 3.5mm audio jack are absent from both. These are standard constraints for modern smartwatches, which are designed to pair exclusively with mobile operating systems rather than desktop platforms.

This group is a complete tie. There is not a single spec in this category that distinguishes one watch from the other, and none of the shared absences represent a meaningful disadvantage in the context of how these devices are typically used. Buyers should weigh other specification groups to inform their decision.