Amazfit Cheetah 2 Ultra Review: GPS, HR, and SmO2 Tested

The Amazfit Cheetah 2 Ultra is a serious endurance watch that costs less than most of its competition. It sits above the Cheetah 2 Pro in Amazfit's lineup, adds an SmO2 sensor, dual-frequency GNSS, and HYROX-specific tooling, and it has now been through enough independent testing to form a clear picture. The numbers are mostly encouraging. A few gaps remain.

Heart Rate Accuracy: Three Tests, Consistent Results

The optical PPG sensor on the Cheetah 2 Ultra has been tested three times now across different conditions, and the pattern is consistent. In a HYROX simulation run at 33°C, the watch matched reference devices with near-zero bias against a Whoop MG worn on the biceps, a Garmin HRM600 chest strap (which reads electrical impulses via ECG), and a Polar Verity Sense optical armband. That is a clean result in the worst kind of environment for wrist-based PPG: heat, mixed-modality effort, grip work, and transitions. The Whoop MG and the Cheetah 2 Ultra were essentially tied on accuracy in that test, which puts the Amazfit ahead of the Fitbit Air, which produced the widest error range of any device in the same session. Three clean HR tests is not luck. The sensor is genuinely reliable. You can find the detailed breakdown across bike, HYROX, and heat conditions in our [HR accuracy deep-dive](/en/articles/amazfit-cheetah-2-ultra-hr-accuracy-bike-hyrox-and-heat-tested-2026-06-01).

GPS Performance: Solid but Not Class-Leading

On a standardised 10-mile GPS accuracy test, the Cheetah 2 Ultra scored 81%. That is better than the Cheetah 2 Pro, which is the right direction of travel. It is behind the Garmin Forerunner 970, which remains the benchmark for GPS accuracy at this price tier. Dual-frequency GNSS is confirmed, so the hardware is there. The 81% figure puts it in the same rough bracket as mid-range Coros watches rather than at the top of the Garmin or Coros Vertix tier. For road running and standard triathlon courses, 81% is workable. For technical trail or point-to-point routes where distance accuracy feeds your pacing strategy, the gap to the Forerunner 970 matters. We covered the GPS data in more detail in our [GPS and trail climb feature test](/en/articles/amazfit-cheetah-2-ultra-gps-battery-and-trail-climb-feature-tested-2026-05-25).

SmO2, HYROX Tools, and the Sensor Stack

The SmO2 sensor is the headline addition over the Cheetah 2 Pro. Muscle oxygen saturation is measured optically, same physical principle as SpO2 but targeted at local muscle tissue rather than blood oxygen at the fingertip. It is useful for pacing high-intensity intervals and tracking recovery between sets, which is exactly what HYROX athletes need. The HYROX-specific workout modes add structured tracking for the eight stations, which Garmin and Coros have not prioritised in the same way. The barometric altimeter reads air pressure for elevation, separate from GPS vertical data, which gives better floor-to-floor accuracy on indoor HYROX venues. The full sensor stack also includes the standard wrist PPG for continuous HR, SpO2 via optical sensor, and dual-frequency GNSS for outdoor position. It is a dense package for the price. The Amazfit Balance Ultra at £599.90 shares some of this positioning but targets more of a hybrid lifestyle-training buyer, as covered in our [Balance 3 vs Balance Ultra breakdown](/en/articles/oura-ipo-garmin-eu-features-amazfit-cheetah-2-pro-june-2026-roundup-2026-05-22).

For triathletes, the swim tracking works and the multi-sport transitions are functional. The Cheetah 2 Pro already handled cycling and swimming reasonably well per our [Cheetah 2 Pro review](/en/articles/amazfit-cheetah-2-pro-review-running-cycling-and-swimming-tested-2026-05-29), and the Ultra builds on that base. Battery life is also not a concern: a 55-hour real-world ride test confirmed the watch can cover a full iron-distance event and then some, as detailed in our [battery test article](/en/articles/amazfit-cheetah-2-ultra-battery-test-55-hours-on-a-real-ride-2026-05-24).

What is missing or disappointing is narrower than the positives but still real. The GPS accuracy gap versus the Forerunner 970 is meaningful if you race on complex courses. The SmO2 implementation is new enough that the algorithm validation against gold-standard devices is not yet comprehensive in the public literature. The Zepp OS ecosystem remains thinner than Garmin Connect or the Polar training load infrastructure for serious periodisation. If you rely on Garmin's Training Readiness scoring or Polar's Orthostatic Test integration, you will feel that absence. The Whoop MG still edges out any wrist-based device for recovery HRV tracking because of consistent placement and the electrical-versus-optical accuracy difference, and the Cheetah 2 Ultra does not change that calculus.

The Cheetah 2 Ultra is the right buy for a Hyrox athlete or hybrid runner-cyclist who wants verified HR accuracy, long battery, SmO2 data, and does not want to pay Forerunner 970 prices. If GPS precision on technical trails is your top priority, look at the Forerunner 970 or Coros Vertix 3 first. If you are already in the Amazfit ecosystem and coming from a Cheetah 2 Pro, the SmO2 sensor and improved GPS make the upgrade case real, not cosmetic.