Where they actually differ
The most decisive specs, ranked by how much they matter — before the full spec table.
| Spec | Amazfit - T-Rex 3 | Garmin - vívoactive 5 |
|---|---|---|
| Battery life | 672 h | 264 h |
| Peak brightness | 2000 nits | 1000 nits |
| Weight | 68 g | 26 g |
| Display size | 1.5 " | 1.2 " |
| Water resistance | 10 ATM | 5 ATM |
Between the T-Rex 3 and vívoactive 5, the T-Rex 3 comes out ahead in battery life / peak brightness, while the vívoactive 5 wins on weight. Overall, the T-Rex 3 scores 62.7 and the vívoactive 5 scores 55.7 on our Mars Score.
Which should you buy?
The T-Rex 3 edges ahead on the Mars Score (62.7 vs 55.7), but the 7.0-point gap is small enough that the right pick comes down to which spec advantages matter to you.
Pick the T-Rex 3 if your top frustration with your current device is running out of charge before the day ends — endurance is the lead spec here. The biggest gaps in its favor are battery life, peak brightness, display size, among others. The single most decisive one: Battery life — 154.55% more. 672 h vs 264 h.
Pick the vívoactive 5 if you carry the device everywhere and weight or thickness has been the deciding factor before. Its strongest claims are weight. The single most decisive one: Weight — 42.00 g less. 26 vs 68.
Both ship with comparable ecg, cellular, spo2, so those specs do not separate the two — focus on the differences below.
Bottom line: the T-Rex 3 is the safer default. The other model is the right choice only when its specific advantages line up with your priorities.
Which should you buy: Amazfit - T-Rex 3 or Garmin - vívoactive 5?
Amazfit - T-Rex 3 leads the current Mars Score by 7.0 points.The more useful decision is the trade-off behind that result: compare display size, battery life against the way you will actually use the product.
Choose Amazfit - T-Rex 3 if…
Amazfit - T-Rex 3 has the measurable edge on battery life h, peak brightness nits, display size in.
Choose Garmin - vívoactive 5 if…
Garmin - vívoactive 5 has the measurable edge on weight g.
This is a structured comparison of the published catalog values. It is not a claim of identical real-world performance across every workload; use the linked spec drill-downs and methodology page to inspect the inputs.
Why Amazfit - T-Rex 3 wins
- ▲Battery life — 154.55% more. 672 h vs 264 h.
- ▲Peak brightness — 100.00% more. 2000 nits vs 1000 nits.
- ▲Display size — 25.00% more. 1.5 " vs 1.2 ".
- ▲Water resistance — 5.00 ATM more. 10 vs 5.
Why Garmin - vívoactive 5 wins
- ▲Weight — 42.00 g less. 26 vs 68.
Spec comparison
Design
| Spec | Amazfit - T-Rex 3 | Garmin - vívoactive 5 |
|---|---|---|
| Case size | 48.5 mmlead | 42 mm |
| Weight | 68 g | 26 glead |
| Case material | polymer | polymer |
| Water resistanceⓘ | 10 ATMlead | 5 ATM |
Display
| Spec | Amazfit - T-Rex 3 | Garmin - vívoactive 5 |
|---|---|---|
| Display size | 1.5 "lead | 1.2 " |
| Always-on display | true | true |
| Peak brightnessⓘ | 2000 nitslead | 1000 nits |
Health & Fitness
| Spec | Amazfit - T-Rex 3 | Garmin - vívoactive 5 |
|---|---|---|
| ECG | false | false |
| SpO2 | true | true |
| Temperature sensor | truelead | false |
| Sleep tracking | true | true |
| Blood pressure | false | false |
Battery & Connectivity
| Spec | Amazfit - T-Rex 3 | Garmin - vívoactive 5 |
|---|---|---|
| Battery lifeⓘ | 672 hlead | 264 h |
| GPS | true | true |
| Cellular | false | false |
| NFC | false | truelead |
| OS | Zepp OSlead | Garmin OS |
Frequently asked
Which has longer battery life, T-Rex 3 or vívoactive 5?+
T-Rex 3 lasts 672 hours vs 264 hours.
Do T-Rex 3 or vívoactive 5 support ECG?+
Neither supports ECG.
Which has cellular, T-Rex 3 or vívoactive 5?+
Neither offers cellular.