Apple is putting new data behind one of its biggest claims for the Apple Watch Series 12 and Apple Watch Ultra 4. The company says the new Health Sensing System delivers the most accurate heart rate sensing in a wearable, and a new study compares the Series 12 directly with several leading smartwatches, fitness trackers and a smart ring.
The study tested the Apple Watch against devices from Garmin, Google, Huawei, Samsung and WHOOP, while an Oura Ring 5 was also included. Apple used a Polar H10 ECG chest strap as the reference measurement to assess heart rate accuracy during workouts and everyday activities.
How Apple Tested The Apple Watch Series 12
Apple’s nine-page study involved 1,460 adults across five testing sites in the US and Malaysia during July and August 2026. A total of 1,254 participants contributed at least one paired measurement to the final analysis.
Each participant wore an Apple Watch Series 12 on one wrist and a competing wrist-based device on the other. The Polar H10 ECG chest strap provided the reference heart rate measurement used to compare the devices.
Apple tested the 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 according to Oura’s recommended placement.
The testing was designed to cover situations that can make wrist-based heart rate sensing difficult. Participants completed outdoor runs, treadmill intervals, cycling, high-intensity interval training and strength workouts.
Apple also measured heart rate during everyday activities including resting, desk work, preparing meals and walking. This gave the company data from both high-intensity exercise and normal daily movement.
Series 12 Showed Better Accuracy Across The Tests
According to Apple’s analysis, the Series 12 delivered statistically better overall heart rate accuracy than every comparison device across both exercise and daily-life measurements.
Across 159 individual activity and measurement comparisons, Apple Watch produced statistically better accuracy in 139. The tests included conditions involving rapid wrist movement and changing heart rates, which can make optical heart rate sensors less reliable.
Apple specifically considered cadence lock during running. This occurs when an optical sensor incorrectly interprets a runner’s movement rhythm as their heart rate, potentially causing the reported pulse to track running cadence rather than the actual heartbeat.
The results are particularly relevant to the new Health Sensing System, which combines updated electrical and optical photoplethysmography, or PPG, sensors with new signal-processing algorithms.
Apple says the system enables new health and fitness features on the Series 12 and Ultra 4, including Recovery HRV and the Readiness app.
Apple Watch Series 12 Health Sensing System
The Health Sensing System is one of the central hardware changes in Apple’s latest watches. Rather than relying on a single sensor improvement, Apple has combined updated sensing hardware with processing designed to interpret heart and health data more accurately.
The new study gives Apple a way to quantify that improvement against other popular wearables instead of relying only on specifications or controlled demonstrations.
The results do not mean that every heart rate reading from an Apple Watch will always be more accurate than another wearable. Instead, Apple’s study reports better statistical accuracy across the specific activities and measurements included in its testing.
The Apple Watch Series 12 is currently available for preorder starting at $399, while the Apple Watch Ultra 4 starts at $799. Both models launch on September 18.
