Amazfit T-Rex Ultra vs Garmin Forerunner 255
The Verdict
Both smartwatches excel at fitness tracking with GPS and heart-rate monitoring, but serve different priorities. Amazfit T-Rex Ultra emphasizes durability with its stainless steel bezel, 10 ATM water resistance for diving, and superior AMOLED display at 454x454 resolution with vibrant colors and true blacks. Battery life reaches an impressive 20 days in smartwatch mode with 80 hours of GPS tracking. Garmin Forerunner 255 counters with exceptional lightness at 49g, broader connectivity through NFC and Wi-Fi, and proven sports-specific software that many runners prefer. Its MIP display offers excellent outdoor visibility and lasts 14 days smartwatch mode or 30 hours GPS. Forerunner 255 excels for serious athletes prioritizing lightweight design and sports features, while T-Rex Ultra suits adventure enthusiasts wanting rugged construction and visual display quality. For most fitness users, Garmin's $100 lower price and refined sports ecosystem make it the stronger choice.
Who Should Buy
Buy the Amazfit T-Rex Ultra if…
- →Excellent 20-day battery life with always-on display
- →Dual-band six-satellite GPS for high accuracy
- →Rugged design with 15 military-grade certifications
Buy the Garmin Forerunner 255 if…
- →14-day battery life means weekly charging at most
- →Multi-band GPS for exceptional outdoor tracking accuracy
- →Morning Report with daily training readiness and HRV status
Category Scores
Pros & Cons
Amazfit T-Rex Ultra
Pros
- Excellent 20-day battery life with always-on display
- Dual-band six-satellite GPS for high accuracy
- Rugged design with 15 military-grade certifications
- Free-diving rated to 45 meters
- Offline maps with route import support
Cons
- No ECG, skin temperature, or NFC payments
- No Wi-Fi or cellular connectivity
- Zepp OS app ecosystem is limited
- Heavier than most smartwatches at 89g
- No third-party app store
Garmin Forerunner 255
Pros
- 14-day battery life means weekly charging at most
- Multi-band GPS for exceptional outdoor tracking accuracy
- Morning Report with daily training readiness and HRV status
- Race Predictor estimates finish times for 5K to marathon
- Lightweight at 49 g and comfortable for 24/7 wear
Cons
- MIP display lacks the vibrancy of AMOLED competitors
- No touchscreen on base model — button-only navigation
- No ECG or blood pressure monitoring
- Limited smart features compared to Apple Watch or Wear OS
- Third-party app ecosystem is small
Full Specifications
| Spec | Amazfit T-Rex Ultra | Garmin Forerunner 255 |
|---|---|---|
| Software | Zepp OS 2.0 | Garmin proprietary OS |
| Body | ||
| Weight | 89 g | 49 g |
| Case material | Stainless steel bezel, fiber-reinforced polymer case | Fiber-reinforced polymer |
| Water resistance | 10 ATM, ISO 22810 certified for free-diving to 45m | 5ATM |
| Health & Sensors | ||
| ECG | ||
| SpO₂ | ||
| Skin temperature | ||
| Heart rate | ||
| Sleep tracking | ||
| Battery | ||
| Battery life | Up to 20 days typical use, 80 hours GPS | Up to 14 days (smartwatch), 30 hrs GPS |
| Display | ||
| Size | 1.39 inch | 46mm |
| Type | AMOLED | MIP (Memory-in-Pixel) transflective |
| Always-on display | ||
| Resolution | 454 x 454 | 260 x 260 |
| Connectivity | ||
| GPS | ||
| NFC | ||
| Wi-Fi | ||
| Cellular | ||
| Bluetooth | 5.0 | 5.0 |
| Processor | ||
| Chipset | — | Garmin custom SoC |
Related Comparisons
This comparison is based on verified manufacturer specifications covering display, performance, camera, battery, and build quality. Scores are generated by analyzing specs across weighted categories on a 10-point scale. Learn more about our methodology.
Explore more in smartwatches, see all Amazfit products or all Garmin products. View full details for the Amazfit T-Rex Ultra or the Garmin Forerunner 255.