Short answer: the Apple Watch Ultra 2 produced the closest heart-rate results to a Polar H10 chest strap in a reported comparison involving selected Garmin, Samsung and Whoop devices. That is meaningful evidence in the tested running workout, but it is not proof that Ultra 2 is the most accurate smartwatch for every sensor, sport or competitor.
The result also needs context: the comparison covered particular models, software and conditions—not every Garmin or Samsung watch—and the Ultra 2 is now an older Apple model alongside the newer Ultra 3.
What the comparison actually tested
Data scientist Rob ter Horst compared the Apple Watch Ultra 2 with a Polar H10 chest strap during an indoor running workout. His wider dataset included the Garmin Forerunner 570, Garmin Fenix 7, Samsung Galaxy Watch 7 and Whoop MG. Sleep data was also compared with a Hypnodyne ZMax sleep-monitoring device.
Coverage of the investigation reported that the Ultra 2 was running watchOS 26 beta. That matters because wearable accuracy depends on algorithms as well as hardware, and beta software can differ from the final public release. The devices were not necessarily worn simultaneously or tested with identical firmware, fit, workout conditions and sensor settings.
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The Polar H10 is a strong consumer reference because a chest strap measures electrical cardiac activity close to the heart. It is still not the same as a clinical ECG or a peer-reviewed, multi-subject laboratory benchmark.
TechRadar’s report and Tom’s Guide’s coverage provide the reported details.
Reported heart-rate results
| Device | Reported comparison | What it means |
|---|---|---|
| Apple Watch Ultra 2 | Closest to the Polar H10 | Best result in this particular test |
| Samsung Galaxy Watch 7 | Approximately 3% deviation | Also comparatively close |
| Whoop MG | Approximately 6% deviation | Useful result, but not a smartwatch comparison on equal terms |
| Garmin Forerunner 570 | Approximately 7% deviation | Applies to this model and test conditions |
| Garmin Fenix 7 | Approximately 9% deviation | Does not represent every Garmin watch or chest-strap setup |
The appropriate conclusion is: the tested Apple Watch Ultra 2 had the smallest reported heart-rate error among the tested devices. It is not: “Apple has definitively beaten Garmin, Samsung and Whoop at heart-rate accuracy.” A single researcher’s protocol cannot establish universal error rates for entire product families.
Why the Ultra 2 result is plausible
The Ultra 2 combines a third-generation optical heart sensor with an electrical heart sensor and Apple’s exercise software. Apple lists ECG functionality and a broad health-sensing package for the watch; hardware and feature availability can vary by region and software version. See Apple’s technical specifications and comparison page.
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When heart-rate precision is critical, a Polar H10 or another compatible chest strap remains the safer choice for structured training, racing and interval work. The Ultra 2’s good wrist result makes it a strong all-rounder; it does not eliminate the advantage of measuring closer to the heart.
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Sleep accuracy is a separate question
The reported sleep comparison found that the Ultra 2 identified REM and deep sleep at approximately 73% agreement with the Hypnodyne ZMax reference, and light sleep at approximately 86.5%. Those figures are encouraging, but they should not be presented as clinical validation.
Sleep technology has several different jobs:
- Sleep duration: usually more useful than exact stage labels.
- Sleep and wake detection: often more dependable than distinguishing individual stages.
- REM, deep and light sleep: algorithmic estimates based on movement and cardiovascular signals.
- Sleep-apnea notifications: screening-oriented alerts, not a diagnosis.
- Recovery scores: software interpretations that can differ substantially between Apple, Garmin, Whoop and Samsung.
Watches do not directly measure brain waves in the way a full polysomnography study does. The ZMax comparison therefore adds useful evidence about one device and one protocol, not a definitive ranking of consumer sleep trackers.
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Sensor accuracy is not one measurement
Heart rate and ECG
Heart-rate accuracy should be judged separately at rest, during steady exercise, intervals, cycling, swimming and resistance training. ECG is different again: the Ultra 2 records a single-lead electrical rhythm tracing, not a full clinical 12-lead ECG. It can support certain health notifications where enabled, but it is not a replacement for medical evaluation.
GPS
The Ultra 2 has precision dual-frequency GPS. That gives it a strong technical basis for tracking in cities, forests and other challenging environments, but the reported heart-rate comparison says nothing about GPS accuracy.
Garmin also offers watches with multi-band or dual-band GNSS. Antenna design, firmware, satellite mode, battery-saving settings and the environment all affect results. Distance, route drift, elevation and pace stability should be tested separately. Garmin may still be preferable for long expeditions because of battery life, maps and navigation controls.
Blood oxygen
Blood-oxygen readings can be affected by fit, movement, cold extremities, circulation and tattoos. Regional restrictions may disable the feature, and consumer readings should not be treated as a medical diagnosis. A sensor being present does not guarantee identical availability in every country.
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- MIL-STD 810H certified, ECG certified, GPS (L1+L5), GLONASS, GALILEO, BDS, Third-generation optical heart sensor, Multiday battery life, up to 36 hours of normal use
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Temperature
Wrist temperature generally indicates changes from a personal baseline rather than core body temperature. It can support trends and cycle-related insights, but it should not be treated as a clinical thermometer.
Motion, altitude and water sensors
Apple lists an always-on altimeter, compass, gyroscope, motion sensors, a depth gauge and water-temperature sensing in addition to heart-rate and temperature hardware. The Ultra 2 supports recreational scuba use to 40 metres according to Apple, but it is not a substitute for dive training, redundant instrumentation or a dedicated dive computer.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Apple Watch Ultra 2 versus the alternatives
Versus Garmin
The Ultra 2 has the stronger result in the cited heart-rate test, but “Garmin” is not one product. Forerunner, Fenix, Epix, Venu and Instinct watches use different hardware, software and intended-use profiles. A Garmin paired with a chest strap is also a fundamentally different heart-rate setup from a Garmin relying only on wrist optics.
Garmin remains compelling for endurance athletes who value multi-day or multi-week battery life, structured workouts, training-load tools, physical buttons, offline maps, multisport support and broad accessory compatibility. Those are workflow advantages, not evidence that Garmin’s wrist sensor is universally more or less accurate.
Versus Whoop
Whoop is primarily a screenless monitoring and coaching platform, not a conventional smartwatch. Its appeal is continuous wear, strain analysis, sleep coaching and recovery trends. Apple offers a display, apps, notifications, cellular options, navigation, ECG hardware and a much broader sensor set.
The products answer different questions. Whoop may suit someone who wants recovery guidance without a watch screen; Ultra 2 suits someone who wants a full smartwatch and health tracker. Whoop’s membership model should be checked on its official site before purchase because plans can change.
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- EXTREMELY RUGGED, INCREDIBLY CAPABLE - 49mm corrosion-resistant titanium case. Larger Digital Crown and more accessible buttons. 100m water resistance. Customizable Action button for instant physical control over a variety of functions.
- BIGGEST, BRIGHTEST DISPLAY YET- A bright Always-On Retina display that’s easy to see, even in direct sunlight. More room for adding complications to customize your watch face.
- FOR ENDURANCE ATHLETES - Advanced metrics in the Workout app, including Heart Rate Zones and Running Form. Precision dual-frequency GPS for accuracy, distance, route, and pace calculations. Trail Loop band is thin, light, and flexible, designed especially for runners.
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Versus Samsung
Apple is the natural choice for iPhone owners, while Samsung is the more direct premium alternative for Android users. Samsung’s Galaxy Watch Ultra2 is a newer product than the Galaxy Watch 7 used in the reported comparison, so the Galaxy Watch 7 result must not be presented as a test of the Ultra2.
Samsung describes features including heart rate, heart-rate variability, respiration, skin temperature, blood oxygen, sleep-related signals and irregular-heart-rhythm notifications. Availability depends on country, compatible phone, app, software and regulatory approval. Consult Samsung’s current product information for the latest details.
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- It turns one heart-rate result into a claim about every sensor.
- It treats Garmin as a single device family with identical accuracy.
- It compares a screenless recovery band with full smartwatches without explaining the category difference.
- It treats a Polar H10 reference as equivalent to clinical ECG.
- It overlooks software versions, workout modes, fit and external-sensor settings.
- It confuses the presence of a sensor with the availability or medical meaning of its output.
Who should buy the Apple Watch Ultra 2?
The Ultra 2 makes the most sense for an iPhone owner who wants a premium smartwatch, strong general heart-rate tracking, ECG capability, safety features, cellular connectivity, a bright display and broad health tools. It is also a sensible all-rounder for recreational runners, cyclists, hikers and gym users who do not want to wear a chest strap every day.
Buy it only at the right price. Apple’s current shop promotes the Apple Watch Ultra 3, so Ultra 2 should now be treated as an older, discounted or refurbished option. Compare its live price with Ultra 3 before buying.
Who should choose something else?
- Serious ultramarathoners and hikers: choose a suitable Garmin if battery life, maps and physical controls matter more than smartwatch integration.
- Android users: consider Samsung or another Android-compatible platform.
- Recovery-first users: consider Whoop if its screenless design and membership model fit your priorities.
- Athletes requiring dependable workout heart rate: add a Polar H10 or equivalent chest strap to whichever watch you choose.
- Buyers wanting Apple’s current flagship: compare Ultra 3 rather than assuming Ultra 2 is still the newest Apple hardware.
Bottom line
The Apple Watch Ultra 2 did win the reported heart-rate comparison against the specific Garmin, Samsung and Whoop devices tested. That makes it a credible choice for strong wrist-based heart-rate tracking, especially for iPhone owners.
It does not prove that Ultra 2 has the best GPS, sleep staging, recovery analysis, battery life or training tools. Choose by ecosystem, sport, battery expectations, subscription tolerance and whether you need a full smartwatch or a focused recovery tracker. For maximum heart-rate confidence, pair any wrist device with a chest strap.
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