Apple's new Watch outpaces the Pixel Watch 4 for heart rate accuracy, but its real rival is missing

The Pixel Watch has spent generations closing the health and fitness gap with established wearables, even becoming a strong Apple Watch alternative for Android users. Apple has now fired back with a heart-rate accuracy study that puts its Series 12 ahead of the Pixel Watch 4 — although Google’s current Pixel Watch 5 never got to compete.

Apple says the Watch Series 12 recorded significantly lower overall heart rate error than every tested rival across workouts and everyday activities. Despite losing the overall contest, the Pixel Watch 4 was among Apple’s closest smartwatch challengers in several measurements. The two watches were statistically inseparable during outdoor cycling under the study’s main Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) calculations.

Google’s older watch even pulled off a small victory during rest, producing more accurate RMSE and MAE results than the Series 12. However, the difference was less than 0.5 beats per minute.

The study’s timing explains the Pixel Watch 5’s absence. Apple tested devices during July and August 2026, but selected rival products commercially available as of June. Google unveiled the Pixel Watch 5 on August 12, after Apple had chosen its competitors.

That doesn’t mean the Pixel Watch 5 would have beaten the Series 12. Google says its latest watch offers 50% more RAM and a 12% CPU performance boost, but its official specifications list the same multi-path optical heart-rate sensor found in the Pixel Watch 4. Google hasn’t claimed the extra processing power improves heart-rate accuracy, which makes sense since the Pixel Watch 5 uses an “Accelerated” Snapdragon W5 Gen 2.

Apple’s hardware upgrades may help explain that advantage. The Series 12 and Ultra 4 introduce a Health Sensing System with updated electrical and optical heart sensors, as well as signal-processing algorithms. It also enables more frequent heart-rate variability readings for the new Recovery HRV and Readiness features. Still, the Pixel Watch 4’s showing makes a current-generation rematch intriguing.

The study also included the Galaxy Watch 8, but Samsung’s newest Galaxy Watch 9 missed out for the same reason as Google’s watch: It arrived after Apple’s June cutoff. Other wearables included the HUAWEI Watch 5, Garmin Forerunner 970, Oura Ring 5, and WHOOP 5.

Apple enrolled 1,460 people across five sites: two near its Cupertino headquarters and locations in San Diego, Austin, and Selangor, Malaysia, of whom 1,254 contributed paired data. Participants wore the Series 12 and a competitor, along with a Polar H10 ECG chest strap, while completing workouts and daily activities.

The study’s scale strengthens Apple’s claim, but the defined lineup limits it. Apple can claim the best heart-rate accuracy among the wearables tested; whether it can outpace the Pixel Watch 5 or Galaxy Watch 9 remains unanswered.