Apple makes a bold claim when it comes to Apple Watch Series 12 and Apple Watch Ultra 4. According to Apple, the new Health Sensing System on both watches “delivers the most accurate heart rate sensing in a wearable.” Apple backs up this claim with a new study that shows how Series 12 heart rate sensing compares to other leading wearables, including smart rings and fitness bands.

Apple Watch Series 12 and Apple Watch Ultra 4 are a major upgrade due to the Health Sensing System that drives many of the health and fitness features.

“With the release of Apple Watch Series 12 and Apple Watch Ultra 4, Apple introduced the Health Sensing System, which includes both updated electrical and optical (photoplethysmography, or PPG) heart sensors and associated signal processing algorithms, as well as several features enabled by the new technology, such as Recovery HRV and the Readiness app,” Apple explains.

According to Apple’s nine-page study, testing took place across five sites in the US and Malaysia during July and August 2026. Apple enrolled 1,460 adults, with 1,254 contributing at least one paired measurement to the final analysis.

Participants wore Apple Watch Series 12 on one wrist and a competing wrist-based device on the other. A Polar H10 ECG chest strap served as the reference.

Apple compared Series 12 against the Garmin Forerunner 970, Google Pixel Watch 4, Huawei Watch 5, Samsung Galaxy Watch 8, and WHOOP 5. Participants also wore an Oura Ring 5 on an index finger, following Oura’s guidance.

The tests covered outdoor running, treadmill intervals, cycling, high-intensity interval training, and strength training. Apple also measured background heart rate during everyday activities including resting, desk work, meal preparation, and walking.

These scenarios included challenges such as rapid wrist movement, changing heart rates, and the “cadence lock” that can cause an optical sensor to mistake running rhythm for a pulse.

Apple says Series 12 produced statistically better overall accuracy than every comparison device across both workouts and daily living. Across 159 individual activity and measurement comparisons, Apple Watch achieved statistically better accuracy in 139.

You can read the study and see the results in full here.

Apple Watch Series 12 is currently available for pre-order from $399. Apple Watch Ultra 4 is available for pre-order from $799. Both models launch in one week on September 18.