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A Ridiculously Tough Smartwatch: Amazfit T-Rex Ultra GPS Review

I really, really tried to destroy this monster. But it really is the best T-Rex yet!

Amazfit T-Rex Ultra GPS(Photo/Josh Wussow)
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Last spring, if you told me I’d soon be excited over a watch named after a theropod, I’d have called you a liar. But a curious thing happened in June of 2022 when a GPS-enabled fossil showed up in the mail. (No, not that kind of Fossil.)

I’m talking about the Amazfit T-Rex 2, one of the most versatile and capable adventure watches in the sub-$400 landscape. And the newest of these is the Amazfit T-Rex Ultra ($399).

 “With features like a stainless steel and mud-resistant design, 30 m freediving support, dual-band GPS and route navigation, ultra-low temperature operation, and 20-day battery life, this smartwatch is the ultimate tool for outdoor enthusiasts,” the brand claims.

You had me at “mud-resistant,” dino fam. Join me as I cover a week’s worth of testing with this metal-clad GPS smartwatch supplied (full disclosure) by Amazfit.  

In short: The Amazfit T-Rex Ultra ($399) is a worthy upgrade to one of my favorite smartwatches of last summer. While the switch to a 316L steel case adds weight to the overall package, the feeling of stability and quality is a perfect match for the watch’s aesthetic. Battery life dips slightly, but the addition of offline map downloads and new adventure-focused workout modes goes a long way toward making the Ultra exactly that.

Amazfit T-Rex Ultra GPS Smart Watch


  • Case Size 47.3 x 47.3 x 13.45 mm
  • Case Material 316L stainless steel & polymer alloy
  • Case Weight 89 g
  • Water Resistance 100 m (30 m freediving)
  • Crystal Glass Material
  • Battery Rating 500 mAh
  • Battery Life 20 days typical, 9 days heavy usage, 20 hours on Accuracy GPS Mode, 80 hours on Endurance GPS mode
  • Band Material Silicone
  • Lug Width 22 mm
  • Connection WLAN 2.4GHz, Bluetooth 5.0 BLE


  • Rugged capability
  • All-weather operation
  • Strong GPS performance
  • Attractive and functional design


  • A little large for small wrists
  • Slightly reduced battery life
  • Zepp App is good, if not great

Amazfit T-Rex Ultra GPS Smart Watch Review

Amazfit T-Rex Ultra GPS review in mud close-up
(Photo Credit/Josh Wussow)

T-Rex Ultra vs. T-Rex 2

Let’s start with what hasn’t changed. Both models use the same 454 x 454-pixel AMOLED screen, covering 1.39 inches with its “glass material” crystal. GPS employs a “dual-band and six satellite positioning system,” and the optical sensor is the same BioTracker 3.0 PPG.

But Amazfit added several extreme sports modes to the Ultra’s quiver, including free diving and sky diving. For more earthbound adventures, the company upgraded the mud resistance of its hardware, along with the switch to a 316L stainless steel case.

There’s also a new slate of offline functionality. Per the marketing copy, “With the Amazfit T-Rex Ultra, you can now search for and download a matching Offline Map of your planned activity area from the Zepp App and match it with your imported route for even better understanding of your surroundings.”

There’s another subtle touch here that deserves to be mentioned: Amazfit’s new method of attaching the silicone strap (which, by the way, is quite comfortable). The hinged dual lugs are a treat, allowing the watch to lay flat on your desk or bedside table. This is something the T-Rex 2 couldn’t do.

Battery and Weight: It’s Complicated

Another thing the Ultra adds is weight: 89 g without the strap versus 66.5 g for the T-Rex 2, strap included.

But honestly, I’m counting this as a positive. The metallic case feels much more substantial, and the difference is immediately recognizable. Note that it says “with” stainless, not “all stainless.” The frame is composed of “polymer alloy,” but for the most part, steel is the medium of choice.

Still, there is one drop worth mentioning, and that’s the battery life. While the previous model was rated for 24 days of typical usage (or 10 days for heavy use; 45 with Battery Saver), the Ultra’s rating dips to 20 days of typical (with 9 of heavy use; 25 days in Battery Saver).

This is a bit perplexing, as the Ultra actually surpasses the T-Rex 2’s battery life when using certain GPS settings. For instance, Accuracy Mode on the new model raises the Ultra’s estimated life to 28 hours versus 26 hours for the T-Rex 2.

There’s also a new “Endurance GPS Mode” with a projected lifespan of 80 hours, which well exceeds the 58-hour mark of its predecessor. It appears that, by putting its batteries in the go-hard adventure basket, Amazfit has lost just a hair of its day-to-day staying power.

Operating System: Zepp 2.0

A note regarding the OS — while Zepp may not be quite as intuitive as its bigger-name competition, it’s a solid, functional platform. The Ultra upgrades to Zepp OS 2.0, which features subtle improvements from the original.

It’s a bit hard to explain, but everything feels smoother, brighter, and more polished. Even water splashes (which used to require that I lock the controls in the shower) seem to be less of a problem without reducing the tactile response of the screen.

Testing the Big Claims

Amazfit places a high emphasis on the cold-blooded nature of the T-Rex Ultra. “Outlast the Ice Age,” the website reads, with a “specially designed circuitry system and battery” good for temperatures as cold as -40 degrees Celcius.

As such, an overnight stay in the freezing rain didn’t phase the watch one bit. Nor did the scalding hot bath it was thrust into during the morning to test its resilience to thermal shocks.

Moving onto a different kind of shock, my impact testing began with a toss from a second-story window. But the snowbank it landed in seemed too soft to draw any real conclusions. Next came the pavement, with a repeated series of lobs and retrievals. Then, I noticed a nice patch of mud near the side of the road.

Amazfit T-Rex Ultra GPS review in mud
(Photo Credit/Josh Wussow)

Yeah, that’s the stuff. Amazfit boasts about the Ultra’s “Mud-resistant Hardware,” and the watch lived up to the billing. But who knows what squirrels or dogs might have done with said mud?

There was only one way to be sure the watch got clean — into the washing machine it went. After a full wash, rinse, and spin, the Ultra showed zero ill effects.

Conclusion: Amazfit T-Rex Ultra GPS Smart Watch Review

Amazfit T-Rex Ultra GPS worn
(Photo/Josh Wussow)

You might notice a lack of negative feedback here. A small reduction in battery life, a few grams of additional weight and, well, that’s more or less it. As a smart-watch skeptic, I expected to find more to complain about.

If the T-Rex 2 made me a believer, the Ultra has made me an enthusiast. I’m generally keen to get back to my simple analog timepieces once the review of a wrist-computer is complete.

But in this case, I genuinely look forward to strapping on this Amazfit when it’s time to hit the gym, the road, or the trail. From its rugged capability and interface to its comfortable, well-considered design, the T-Rex Ultra, you might say, earns its bones.

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