Xiaomi Watch S4

Name: Xiaomi Watch S4
Brand: Xiaomi
SKU: 9711

Manufacturer: Xiaomi

The Xiaomi Watch S4 is a feature-rich smartwatch that brings together connectivity, health monitoring, and a refined design in a 44.5 g body. Its 1.43″ AMOLED Always-On Display renders at 466 x 466 px with a pixel density of 326 ppi, protected by sapphire glass and housed in a case measuring 47.3 x 47.3 x 12 mm. The band is user-replaceable, and the watch carries a 5 ATM waterproof rating down to 50 m, making it suitable for swim tracking complete with stroke counting.

On the health and sensor side, the Watch S4 includes a heart rate monitor, pulse oximeter, body temperature sensor, barometer, gyroscope, accelerometer, and compass, alongside HRV tracking and VO2 max measurement. GPS with Galileo support enables route and elevation tracking, while fall detection and fast or slow heart rate notifications add a safety dimension. Connectivity covers Bluetooth 5.3, NFC, and a single eSIM for cellular use, and the 486 mAh battery is rated for 15 days of typical use with wireless charging supported. Internally, the watch carries 32 GB of storage, includes a microphone for call handling and voice commands, and pairs with a free, ad-free app that covers sleep reports, goal setting, ovulation prediction, water intake, and calendar sync.

Pros

Sapphire glass display offers solid scratch resistance for daily wear
Built-in eSIM with cellular support allows the watch to function independently without a paired phone
A comprehensive sensor suite covering heart rate, SpO2, body temperature, barometer, gyroscope, accelerometer, and compass supports detailed health and fitness monitoring
32 GB of internal storage provides ample space for music and data directly on the device
The 486 mAh battery is rated for up to 15 days, reducing how often the watch needs to be charged
Wireless charging eliminates the need for a physical charging connector

Cons

Wi-Fi is not supported, limiting connectivity options when Bluetooth range is exceeded
No ECG technology or irregular heart rate warnings, leaving out features that some health-focused users may require
A cadence sensor is absent, which affects usefulness for cyclists who track pedaling rate
The watch is not designed for diving, restricting underwater use to surface swimming within its 50 m waterproof rating
No smart alarm function, which some sleep-aware users may find useful

Who is this for?

This watch is well-suited to health-conscious users who want thorough biometric tracking on their wrist, given its combined support for HRV, VO2 max, SpO2, body temperature, resting heart rate, and readiness level monitoring. Those who swim regularly will appreciate the waterproof rating up to 50 m and the built-in stroke counter, while runners and outdoor enthusiasts benefit from GPS with Galileo support, elevation tracking, and fast GPS lock. Users who want a watch that can operate independently from their phone will find the eSIM and cellular module particularly practical, and the 15-day battery life makes it a strong option for those who prefer not to charge frequently. The sapphire glass display and replaceable band add durability and flexibility for everyday wear.

Who is this NOT for?

Users who rely on clinical-grade cardiac monitoring will find this watch lacking, as it does not support ECG technology or irregular heart rate warnings. Cyclists who depend on cadence data will need a separate device, since no cadence sensor is included. Those who work extensively on desktop platforms will face limitations, as the watch is not compatible with Windows or Mac OS X. Divers and those who need deeper water resistance beyond surface swimming should look elsewhere, as the watch is not designed for diving. Users who want a connected experience over Wi-Fi rather than Bluetooth or cellular will also find the absence of Wi-Fi support a practical drawback.

Design:

screen size	1.43"
Display type	OLED/AMOLED
water resistance	Waterproof
ATM rating	5 ATM
waterproof depth rating	50 m
Always-On Display	✓
pixel density	326 ppi
resolution	466 x 466 px
Watch band is replaceable	✓
has branded damage-resistant glass	✕
thickness	12 mm
weight	44.5 g
height	47.3 mm
width	47.3 mm
Has a display	✓
has a touch screen	✓
Has sapphire glass display	✓
volume	26.84748 cm³
is designed for kids	✕

The Xiaomi Watch S4 features a 1.43″ AMOLED touchscreen with a resolution of 466 x 466 px and a pixel density of 326 ppi, and it supports an Always-On Display mode. The screen is protected by sapphire glass, though no branded damage-resistant glass is included. Measuring 47.3 x 47.3 x 12 mm and weighing 44.5 g, the watch has a volume of 26.84748 cm³ and comes with a replaceable band. It carries a 5 ATM waterproof rating with a depth tolerance of 50 m, and it is not designed for kids.

Sensors:

Monitors blood oxygenation levels	✓
Has a heart rate monitor	✓
has GPS	✓
has an accelerometer	✓
Has a temperature sensor	✓
has a compass	✓
Has a barometer	✓
has a gyroscope	✓
Has a cadence sensor	✕
Monitors perspiration	✕

The watch includes a broad set of sensors for health and navigation purposes, covering a heart rate monitor, pulse oximeter for blood oxygenation tracking, and a body temperature sensor. Motion and orientation data are handled by an accelerometer, gyroscope, and compass, while a barometer is also on board. GPS is supported for location-based tracking. A cadence sensor and perspiration monitor are not included.

Activity tracking:

Tracks your sleep	✓
Tracks distance	✓
Tracks steps taken	✓
Measures pace	✓
Provides sleep reports	✓
Detects activities automatically	✓
Has a route tracker	✓
Tracks elevation	✓
Has exercise tagging	✓
Has a stroke counter for swimming	✓
Tracks calorie intake	✓
Designed for diving	✕

The watch covers a wide range of activity tracking capabilities, including steps, distance, pace, elevation, and route tracking, along with automatic activity detection and exercise tagging. Sleep tracking is supported and accompanied by detailed sleep reports. For aquatic workouts, a swim stroke counter is available, though the watch is not designed for diving. Calorie intake tracking rounds out the feature set, allowing users to log food consumption alongside their physical activity data.

Connectivity:

has a cellular module	✓
Is compatible with iOS	✓
Is compatible with Android	✓
Bluetooth version	5.3
supports Wi-Fi	✕
supports ANT+	✕
SIM cards	1 eSIM
has NFC	✓
supports Galileo	✓

The watch includes a cellular module with a single eSIM, allowing it to operate independently of a paired phone, and it is compatible with both iOS and Android. Wireless communication is handled via Bluetooth 5.3 and NFC, while satellite positioning also includes Galileo support. Wi-Fi and ANT+ are not supported.

Battery:

battery life	15 days
battery power	486 mAh
has wireless charging	✓
has a rechargeable battery	✓
Has a solar power battery	✕
has a removable battery	✕

The watch is powered by a rechargeable 486 mAh battery with a rated life of 15 days, and it supports wireless charging. The battery is not removable and there is no solar charging capability.

Features:

has HRV tracking	✓
measures VO2 max	✓
measures resting heart rate	✓
has fast/slow heart rate notifications	✓
shows readiness level	✓
Can be used to answer calls	✓
Locates your phone	✓
Has call control	✓
Has notifications	✓
has irregular heart rate warnings	✕
Has ECG technology	✕
Has silent alarm	✓
Has vibrating alerts	✓
has fall detection	✓
Has a stopwatch	✓
Has smart alarm	✕
has voice commands	✓
internal storage	32GB
Has a built-in camera remote control function	✓
Acquires GPS faster	✓
warranty period	1 years
number of microphones	1
has a front camera	✕

On the health monitoring side, the watch tracks HRV, resting heart rate, and VO2 max, and it displays a readiness and recovery level. Fast and slow heart rate notifications are supported, along with fall detection, though irregular heart rate warnings and ECG technology are not available. For everyday use, it delivers wrist notifications, call control, the ability to answer calls directly from the wrist using its single microphone, voice commands, and a phone-finding function. Alerts are handled through vibration and a silent alarm, while a smart alarm is not included. The watch also features a stopwatch, 32 GB of internal storage, a built-in camera remote shutter, and fast GPS lock. There is no front camera. The device comes with a one-year warranty.

App & Software:

Provides activity reports	✓
Has inactivity alerts	✓
Counts how many calories you've burned	✓
Has goal setting	✓
Has achievements	✓
Free app	✓
Has exercise diary	✓
Ad-free	✓
Has coaching	✕
Has temperature tracking	✓
Has period notifications	✓
Supports routes	✕
Syncs with existing calendars	✓
Has music playback	✓
Exports to email	✕
Includes maps	✓
Doesn’t require account	✕
Predicts ovulation	✓
Predicts start date	✓
Supports widgets	✓
Can be personalised	✓
Has barcode scanner on app	✕
Tracks water intake	✓
Has weight tracking	✓

The companion app is free and ad-free, and an account is required to use it. It covers activity reports, calorie burn tracking, an exercise diary, goal setting, inactivity alerts, and achievements, along with water intake and weight tracking. Women's health features include period notifications, ovulation prediction, and cycle start date prediction. Temperature tracking, maps, calendar sync, music playback, and widget support are also available, and the app can be personalised. Route support and email export are not included, nor is a barcode scanner or in-app coaching.

Miscellaneous:

has a battery level indicator	✓
Has passcode	✓
Is compatible with Windows	✕
has an external memory slot	✕
Is compatible with Mac OS X	✕
has a socket for a 3.5 mm audio jack	✕

The watch includes a battery level indicator and supports passcode protection for security. It does not offer an external memory slot, a 3.5 mm audio jack, or compatibility with Windows or Mac OS X.

Final Verdict

The Xiaomi Watch S4 presents a well-rounded smartwatch proposition built around an extensive health sensor suite, cellular independence via eSIM, and a 15-day battery life that sets a practical standard for daily use. Its sapphire glass display, swim tracking capability, and broad activity monitoring features make it a genuinely capable device for fitness-oriented users and those who want consistent connectivity without relying on a paired phone. While it stops short of offering ECG support, irregular heart rate warnings, or cadence tracking, these omissions are offset by the depth of what it does provide across health, navigation, and communication. For users seeking a feature-complete smartwatch that balances health monitoring with everyday practicality, the Watch S4 makes a compelling case.