Xiaomi Watch S4 vs Google Fitbit Air
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Quick comparison
At a glance
Key specifications and important differences. Full details follow below.
| Feature |  Xiaomi Watch S4 |  Google Fitbit Air |
|---|---|---|
| Price | KSh 20,000.00 | KSh 21,500.00 |
| Display | 1.43-inch AMOLED, 60 Hz | — |
| Battery capacity | 486 mAh | — |
| Water resistance | 5 ATM rated for suitable shallow-water activities | Water-resistant to 50 m; dry the band after exposure to water |
| Operating system | Xiaomi HyperOS 2 | — |
| Positioning / GNSS | Built-in GPS, Galileo, GLONASS, BeiDou and QZSS | — |
| Health & wellness features | Heart rate, blood oxygen, stress, breathing and activity tracking; wellness data is not intended for medical diagnosis | Heart rate, SpO2, skin-temperature variation and fitness tracking; wellness data is not a medical diagnosis |
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Full specifications
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Identity & design
| Specification | Xiaomi Watch S4 | Google Fitbit Air |
|---|---|---|
| Brand | Xiaomi | — |
| Model | Xiaomi Watch S4 | Fitbit Air |
| Announced | March 2025 (global model) | — |
| Dimensions | 47.3 × 47.3 × 12.0 mm (strap and protrusions excluded) | 34.9 × 17 × 8.3 mm without band |
| Weight | Approximately 44.5 g (strap excluded) | 5.2 g without band; 12 g with band |
| Build materials | Aluminum-alloy frame with interchangeable bezel | Recycled polycarbonate and PBT plastic tracker housing |
| Wrist size | Black/Silver: approximately 140–210 mm; Rainbow: approximately 135–210 mm | 130–210 mm textile; 130–175 mm small silicone or 165–210 mm large silicone |
| Strap / band | Fluororubber; Rainbow configuration also includes nylon strap | Textile and polyurethane band with stainless-steel buckle; silicone small and large bands are also supported. |
| Controls / buttons | Rotating crown, side control, interchangeable bezel interaction, and touchscreen | Screenless tracker with vibration feedback and an LED status light; configuration and detailed results are managed in the Google Health app. |
Display
| Specification | Xiaomi Watch S4 | Google Fitbit Air |
|---|---|---|
| Display | 1.43-inch AMOLED, 60 Hz | — |
| Screen resolution | 466 × 466 pixels (~326 ppi) | — |
| Display features | Always-on display; up to 1,500 nits HBM | — |
Performance & software
| Specification | Xiaomi Watch S4 | Google Fitbit Air |
|---|---|---|
| Operating system | Xiaomi HyperOS 2 | — |
Connectivity
| Specification | Xiaomi Watch S4 | Google Fitbit Air |
|---|---|---|
| Bluetooth | Bluetooth 5.3 | Bluetooth 5.0 BLE; syncing range up to 9 m; synchronization requires an internet connection and phone location permission. |
| NFC | Supported; availability varies by region | — |
| Positioning / GNSS | Built-in GPS, Galileo, GLONASS, BeiDou and QZSS | — |
Audio & communication
| Specification | Xiaomi Watch S4 | Google Fitbit Air |
|---|---|---|
| Speaker | Built-in speaker | — |
| Microphone | Two built-in microphones | — |
| Calling | Bluetooth calling when paired with a compatible phone; third-party app voice calls not supported | — |
Sensors, health & fitness
| Specification | Xiaomi Watch S4 | Google Fitbit Air |
|---|---|---|
| Sensors | Heart-rate/blood-oxygen sensor, accelerometer, gyroscope, ambient-light sensor, electronic compass, barometer and Hall sensor | Optical heart-rate sensor, red and infrared SpO2 sensors, and skin-temperature sensor |
| Health & wellness features | Heart rate, blood oxygen, stress, breathing and activity tracking; wellness data is not intended for medical diagnosis | Heart rate, SpO2, skin-temperature variation and fitness tracking; wellness data is not a medical diagnosis |
| Sleep tracking | Sleep monitoring supported | Sleep duration and health insights through Google Health |
| Sports / workout modes | More than 150 sports modes | Automatic and app-started workout tracking |
| Training & outdoor features | — | Live heart-rate broadcast to compatible gym equipment, Cardio Load, Active Zone Minutes, phone-connected GPS and post-workout pace and heart-rate zones in Workout Intensity Map. |
Battery & durability
| Specification | Xiaomi Watch S4 | Google Fitbit Air |
|---|---|---|
| Battery capacity | 486 mAh | — |
| Battery life | Up to 15 days typical use; actual life varies by settings and use | Up to 7 days |
| Charging | 2-pin magnetic charging dock | USB-C charging cable |
| Water resistance | 5 ATM rated for suitable shallow-water activities | Water-resistant to 50 m; dry the band after exposure to water |
Compatibility
| Specification | Xiaomi Watch S4 | Google Fitbit Air |
|---|---|---|
| Phone compatibility | Android 8.0 or later; iOS 14.0 or later | Google Account and Google Health app required; Android 11.0+ or iOS 16.4+ |
| Companion app | Mi Fitness | Google Health app |
| Colors | Black, Silver, or Rainbow depending on configuration | Obsidian, Berry, Lavender or Fog; special editions vary |
Additional specifications
| Specification | Xiaomi Watch S4 | Google Fitbit Air |
|---|---|---|
| Vibration motor | — | Vibration motor |
| Charging time | — | 90 minutes; 5-minute quick charge provides up to 1 day |
| Movement sensors | — | 3-axis accelerometer and gyroscope |
| Bluetooth and Wi-Fi | — | Bluetooth 5.0; Bluetooth LE sync up to 9 m |
| Packing list | — | Google Fitbit Air tracker, wristband and USB-C charging cable |
| Smart recognition | — | Automatically detects common activities |
| Energy, load and readiness features | — | Personalized insights available through Google Health and optional Google Health Premium |
| strap material | — | Textile performance band with stainless-steel buckle; silicone bands optional |
| temperature monitoring | — | Skin-temperature variation in the Google Health app |
| offline storage | — | 7 days of detailed minute-by-minute motion data and 30 days of daily totals |
| packaging materials | — | 100% plastic-free packaging |
| Positioning / GPS | — | Phone-connected GPS through the Google Health app; Fitbit Air does not have built-in GPS. |
| Health & wellness features | — | 24/7 heart rate, resting heart rate, heart-rate variability, breathing rate, blood oxygen (SpO2), skin-temperature variation, steps, distance, calories, Active Zone Minutes, Cardio Load and Readiness; Google Health also supports weight, nutrition, water, mood and cycle logging. |
| Sleep tracking | — | Sleep Score, sleep schedule, sleep duration and sleep stages; Smart Wake uses sleep movement and heart rate to wake during a lighter sleep stage; adaptive sleep coaching requires Google Health Premium. |
| Sports / workout modes | — | Automatic detection for walking, running, cycling, sports, elliptical, rowing machine and stationary bike; manual and app-started workout tracking is also supported. |
| Smart features / notifications | — | Vibration and LED battery/status alerts, optional phone notifications, Fast Pair on Android and multi-device support with a compatible Pixel Watch. |
| Charging | — | Magnetic USB-C charging cable; 0–100% in 90 minutes; a 5-minute quick charge provides up to one day of battery life. |
| Colors | — | Obsidian with Matte Black buckle; Berry with Polished Champagne Gold buckle; Lavender or Fog with Polished Silver buckle; Stephen Curry Rye/Pyrite and Pokémon Sleep Sleepy Blue special editions. |
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