In a controlled run test, both premium wearables stayed within a few bpm of a chest monitor, underscoring reliable heart-rate tracking.
A head-to-head test compares the Apple Watch Ultra 4 and the Garmin Fenix 9 Pro to a chest-based heart-rate monitor during a 30-minute run. Both watches stayed within two beats per minute of the chest strap, showing solid heart-rate tracking. Garmin shines with longer battery life, while Apple leans into a broader smartwatch experience. For most people, either watch provides reliable heart-rate data, with the choice coming down to daily-use habits and charging needs.
What to know now:
A new side-by-side test pits the Apple Watch Ultra 4 against the Garmin Fenix 9 Pro to see which wrist wearable lines up best with a chest-based heart-rate monitor. In a 30-minute run, both watches stayed within two beats per minute of the ECG reference, indicating a high level of consistency for heart-rate tracking.
Those tiny gaps matter mainly for serious training, where precise pace and effort matter. The test found the two devices telling a very similar story about how the body was performing during the workout, even though their sensors and processing engines differ.
Beyond heart rate, the watches differ in day-to-day use. The Garmin tends to offer longer battery life and tougher outdoor tools, while the Apple Watch Ultra 4 provides a richer software experience with more apps and everyday smart features. Your pick may come down to whether you want longer runs between charges or a broader smartwatch ecosystem on your wrist.
In this test, the Garmin Fenix 9 Pro measured 159 bpm and the Apple Watch Ultra 4 measured 160 bpm, with the chest strap at 158 bpm. Both are strong performers for everyday workouts, showing reliable heart-rate parity with professional-grade monitoring.
Calorie estimates varied, but readings stayed close enough to be useful for general workout trends. The study focused on heart-rate parity rather than calories, so use these numbers as a guide to relative effort rather than exact energy burn.
Choose Garmin if you want endurance-ready tools and longer battery life for long sessions outdoors. Opt for the Apple Watch Ultra 4 if you value a polished software experience, a broad app ecosystem, and everyday health tracking beyond workouts.
For most runners, either watch will deliver dependable heart-rate data during workouts. If you regularly go on long outdoor trips, the Garmin may reduce charging breaks. If you want a more feature-rich smartwatch that works well with your iPhone, the Apple Watch Ultra 4 is a solid pick.
Both models will likely receive ongoing software updates that tweak health tracking and apps. Your decision may hinge on how you use your watch daily and how long you’re willing to go between charges.
Both were within two bpm of the chest strap reference, showing strong accuracy.
Garmin Fenix 9 Pro generally offers longer battery life, aiding longer runs or outdoor trips.
Yes. Apple provides a richer app and notification experience, while Garmin focuses on rugged, outdoor-oriented tools.
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