Apple Watch Ultra 3 vs Xiaomi Watch S4
Size, specs & wrist fit compared
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Which one fits you
On wrists narrower than about 52mm, the Xiaomi Watch S4 is the safer pick — it stays proportionate down to roughly 50mm, where the Apple Watch Ultra 3 starts to hang over the edge. Above 52mm both sit cleanly, and the Apple Watch Ultra 3 gives you more presence.
The Xiaomi Watch S4 wears larger than the Apple Watch Ultra 3 (47.3mm vs 44mm case), giving it more wrist presence — and needing a wider wrist to sit cleanly.
On the wrist the Xiaomi Watch S4 feels lighter (44.5g vs 61.8g, case only).
The Apple Watch Ultra 3 is thinner than 89% of the 44mm watches we track and the Xiaomi Watch S4 than 92% of the 47mm ones — so both wear flatter than their widths suggest.
The Xiaomi Watch S4 is 3.3mm wider, 1.7mm shorter and 17.3g lighter than the Apple Watch Ultra 3.
Apple
Watch Ultra 3
Xiaomi
Watch S4
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Apple
Watch Ultra 3
Xiaomi
Watch S4
Watch Fit Tool
For sports watches, lug-to-lug (L2L) is what matters most — it decides whether a watch overhangs your wrist. Bulky is fine; overhang is not.
Measure at the point where you wear your watch — typically just below the wrist bone.
Flat width — lay your arm on a table, palm facing up, and measure straight across the top of your wrist with a ruler. Bone to bone; do not follow the curve down the sides.
Around — wrap a tape measure snugly round the wrist. No tape? Wrap a strip of paper, mark the overlap and hold the strip against a ruler.
Width ≠ circumference. They are different numbers — around 170mm is about 64mm across — so set the toggle to whichever one you actually measured before you type it in.
Apple Watch Ultra 3
Case 49.0mm · Lug-to-lug 49.0mm · Thickness 12.0mm · 62g
Sweet Spot
49mm on a 55mm wrist
Across the wrist it works — 3.0mm spare each side — but wide enough that the edge of the case back lifts clear of the skin.
On a 55mm wrist the sweet spot is 47–53mm lug to lug. This one is 49mm.
Measure where you wear it, just below the wrist bone. Either of these works — the tool converts between them.
- 1. Flat width — arm flat on a table, palm up. Measure straight across the top of the wrist, bone to bone, ignoring the curve down the sides.
- 2. Around — a tape, or a strip of paper marked and held against a ruler, snug the whole way round.
Leather: Attaches at the lugs, so the case back rests on your skin. Thins and softens with wear. Typical figures, not this model’s own.
Show the measurementsHide the measurements
- Across the wrist3.0mm spare each side
Fills the wrist without reaching the edge.
- Off the wrist12.0mm off the skin
Normal sports-watch height for a wrist this size. (12.0mm case, back against the skin)
- How it seats~7.3mm under the rim
Wide enough that the edge of the case back lifts clear of the skin.
- Weight on the wrist62g
Substantial without being a burden — the usual weight of a steel watch on a wrist this size. (1.1g per mm of wrist)
Xiaomi Watch S4
Case 47.3mm · Lug-to-lug 47.3mm · Thickness 12.0mm · 45g
Sweet Spot
47.3mm on a 55mm wrist
Across the wrist it works — 3.9mm spare each side — but wide enough that the edge of the case back lifts clear of the skin.
On a 55mm wrist the sweet spot is 47–53mm lug to lug. This one is 47.3mm.
Measure where you wear it, just below the wrist bone. Either of these works — the tool converts between them.
- 1. Flat width — arm flat on a table, palm up. Measure straight across the top of the wrist, bone to bone, ignoring the curve down the sides.
- 2. Around — a tape, or a strip of paper marked and held against a ruler, snug the whole way round.
Leather: Attaches at the lugs, so the case back rests on your skin. Thins and softens with wear. Typical figures, not this model’s own.
Show the measurementsHide the measurements
- Across the wrist3.9mm spare each side
Fills the wrist without reaching the edge.
- Off the wrist12.0mm off the skin
Normal sports-watch height for a wrist this size. (12.0mm case, back against the skin)
- How it seats~6.3mm under the rim
Wide enough that the edge of the case back lifts clear of the skin.
- Weight on the wrist45g
Light enough to forget you have it on. (0.8g per mm of wrist)
2D Dimension Schematics
Every case drawn to scale on a shared centre — from above, and in profile against the wrist.
- Apple Watch Ultra 344mm × 49mm · 12mm thick
- Xiaomi Watch S447.3mm · 12mm thick
3D preview
Apple Watch Ultra 3 vs Xiaomi Watch S4 on a wrist
Sized to your own wrist, turned any way you like.
Shapes are built from published measurements, not manufacturer 3D models — accurate proportions, generic dial.
Battery life compared
Furthest apart in Smartwatch mode, where the Xiaomi Watch S4 lasts 8.6× as long as the Apple Watch Ultra 3 (15 days against 42 hours).
Apple Watch Ultra 3Xiaomi Watch S4
Smartwatch
1.75 days15 daysBattery Saver
72 hours—
Specifications
The short version
11 key specs| Spec | AppleWatch Ultra 3 | XiaomiWatch S4 |
|---|---|---|
| Case Width | 44mm | 47.3mm |
| Lug-to-Lug | 49mm | 47.3mm |
| Thickness | 12mm | 12mm |
| Weight | 61.8g | 44.5g |
| Shape | Rectangle | Circular |
| Water Resistance | 10 ATM | 5 ATM |
| GPS | Yes | Yes |
| Display type | OLED/AMOLED | OLED/AMOLED |
| Screen size | 1.98 inches | 1.43 inches |
| Battery life | 1.75 days | 15 days |
| Released | 2025 | 2024 |
Every specification
120 specs| Spec | Apple Watch Ultra 3 | Xiaomi Watch S4 |
|---|---|---|
| Design | ||
| width | 44 | 47.3 |
| height | 49 | 47.3 |
| volume | 25.87 cm³ | 26.85 cm³ |
| weight | 61.8 g | 44.5 g |
| thickness | 12 | 12 |
| ATM rating | 10 ATM | 5 ATM |
| resolution | 422 x 514 px | 466 x 466 px |
| screen size | 1.98 inches | 1.43 inches |
| Display type | OLED/AMOLED | OLED/AMOLED |
| Has a display | Yes | Yes |
| pixel density | 326 ppi | 326 ppi |
| water resistance | Waterproof | Waterproof |
| Always-On Display | Yes | Yes |
| has a touch screen | Yes | Yes |
| is designed for kids | No | No |
| waterproof depth rating | 100 m | 50 m |
| Watch band is replaceable | Yes | Yes |
| Has sapphire glass display | Yes | Yes |
| maximum operating temperature | 55 °C | — |
| Ingress Protection (IP) rating | IPX6 | — |
| has branded damage-resistant glass | No | No |
| lowest potential operating temperature | -20 °C | — |
| Battery | ||
| charge time | 1.5 hours | — |
| battery life | 1.75 days | 15 days |
| has wireless charging | Yes | Yes |
| has a removable battery | No | No |
| Has a solar power battery | No | No |
| has a rechargeable battery | Yes | Yes |
| battery life in power save mode | 72 hours | — |
| battery power | — | 486 mAh |
| Sensors | ||
| has GPS | Yes | Yes |
| has a compass | Yes | Yes |
| Has a barometer | Yes | Yes |
| has a gyroscope | Yes | Yes |
| Has a cadence sensor | No | No |
| has an accelerometer | Yes | Yes |
| Monitors perspiration | No | No |
| Has a heart rate monitor | Yes | Yes |
| Has a temperature sensor | Yes | Yes |
| Monitors blood oxygenation levels | Yes | Yes |
| Features | ||
| RAM | 2GB | — |
| release date | 2025-09-09 | 2024-10-29 |
| Has a stopwatch | Yes | Yes |
| Has smart alarm | No | No |
| warranty period | 1 years | 1 years |
| Has call control | Yes | Yes |
| Has silent alarm | Yes | Yes |
| has HRV tracking | Yes | Yes |
| internal storage | 64GB | 32GB |
| measures VO2 max | Yes | Yes |
| Has notifications | Yes | Yes |
| Has ECG technology | Yes | No |
| Locates your phone | Yes | Yes |
| has a front camera | No | No |
| has fall detection | Yes | Yes |
| has voice commands | Yes | Yes |
| Acquires GPS faster | Yes | Yes |
| Has vibrating alerts | Yes | Yes |
| number of microphones | 1 | 2 |
| Can be used to answer calls | Yes | Yes |
| measures resting heart rate | Yes | Yes |
| has irregular heart rate warnings | Yes | No |
| has fast/slow heart rate notifications | Yes | Yes |
| Has a built-in camera remote control function | Yes | Yes |
| shows readiness level | — | Yes |
| Connectivity | ||
| has NFC | Yes | Yes |
| SIM cards | 1 eSIM | 1 eSIM |
| Wi-Fi version | Wi-Fi 4 (802.11n) | — |
| supports ANT+ | No | No |
| supports Wi-Fi | Yes | No |
| supports Galileo | Yes | Yes |
| Bluetooth version | 5.3 | 5.3 |
| has a cellular module | Yes | Yes |
| Is compatible with iOS | Yes | Yes |
| Is compatible with Android | No | Yes |
| Miscellaneous | ||
| has aptX | No | — |
| Has passcode | Yes | Yes |
| Has auto pause | Yes | — |
| has crash detection | Yes | — |
| Is compatible with Windows | No | No |
| Is compatible with Mac OS X | No | No |
| has an external memory slot | No | No |
| Compatible with smart scales | Yes | — |
| has a battery level indicator | Yes | Yes |
| has a socket for a 3.5 mm audio jack | No | No |
| Compatible with external heart rate monitors | Yes | — |
| App & Software | ||
| Ad-free | Yes | Yes |
| Free app | Yes | Yes |
| Has coaching | No | No |
| Includes maps | Yes | Yes |
| Supports routes | Yes | No |
| Has achievements | Yes | Yes |
| Has goal setting | Yes | Yes |
| Has exercise diary | Yes | Yes |
| Predicts ovulation | Yes | Yes |
| Can be personalised | Yes | Yes |
| Has weight tracking | Yes | Yes |
| Predicts start date | Yes | Yes |
| Tracks water intake | Yes | Yes |
| Has inactivity alerts | Yes | Yes |
| Has period notifications | Yes | Yes |
| Has temperature tracking | Yes | Yes |
| Provides activity reports | Yes | Yes |
| Displays fertile window notifications | Yes | — |
| Counts how many calories you've burned | Yes | Yes |
| Doesn’t require account | — | No |
| Activity tracking | ||
| Measures pace | Yes | Yes |
| Tracks distance | Yes | Yes |
| Tracks elevation | Yes | Yes |
| Designed for golf | No | — |
| Tracks your sleep | Yes | Yes |
| Tracks steps taken | Yes | Yes |
| Designed for diving | Yes | No |
| Has a route tracker | Yes | Yes |
| Has exercise tagging | Yes | Yes |
| Has multi-sport mode | Yes | — |
| Tracks calorie intake | No | Yes |
| Provides sleep reports | Yes | Yes |
| Detects activities automatically | Yes | Yes |
| Has a stroke counter for swimming | Yes | Yes |
Wrist Fit
Apple Watch Ultra 3
Sits best on wrists ~52–70mm wide (≈ 13.9–18.7cm circumference).
Xiaomi Watch S4
Sits best on wrists ~50–68mm wide (≈ 13.4–18.2cm circumference).
Frequently Asked Questions
Is the Apple Watch Ultra 3 bigger than the Xiaomi Watch S4?
The Xiaomi Watch S4 is bigger — 47.3mm vs 44mm case width.
Which fits a smaller wrist better, the Apple Watch Ultra 3 or the Xiaomi Watch S4?
The Apple Watch Ultra 3 suits wrists around 52–70mm wide, and the Xiaomi Watch S4 around 50–68mm. The one with the smaller lower bound is the safer pick for a small wrist.
Can I see the Apple Watch Ultra 3 and Xiaomi Watch S4 side by side at true scale?
Yes — the schematics and photos above show both watches at matched scale, and our fit tool overlays each on your wrist width.