Pixel Watch vs Galaxy Watch: Which Is More Accurate?

In 45 healthy adults tested at rest, under mental stress and while walking in neutral, hot and cold rooms, Pixel Watch 2 reached a mean absolute error of 4.9 beats per minute, a 6.7 percent average error and a concordance of 0.87 against an ECG chest strap, and the authors named it and the Fitbit Charge 6 the most reliable of the 10 devices (JMIR Formative Research, 2026). In 34 people on a treadmill, Pixel Watch 3 was off by 2.39 beats per minute on average, a 2.73 percent error (PLOS One, 2026). In 23 healthy adults, the Galaxy Watch Active2 overestimated heart rate by 3.84 beats per minute overall against a Holter ECG, with larger errors during rest and typing than during exercise (JMIR Formative Research, 2022).

A multicentre sleep-lab study in 75 participants compared 11 consumer sleep trackers, including Pixel Watch and Galaxy Watch 5, against polysomnography. Stage agreement ranged widely across the 11, and the authors named Pixel Watch and Fitbit Sense 2 as the stronger wearables for deep sleep (JMIR mHealth and uHealth, 2023). In a separate study of 32 healthy adults, the Galaxy Watch 3 overestimated total sleep by 9.5 minutes, caught 95.4 percent of sleep but only 52.4 percent of wake, and classified the four sleep stages with 65.1 percent accuracy, with REM not reliably estimated (Journal of Sleep Medicine, 2023).

In 152 adults with known or likely sleep apnea, each wearing a Galaxy Watch through two sleep-lab nights, the watch detected moderate-to-severe apnea with an area under the curve of 0.94, 94.1 percent sensitivity and 66.7 percent specificity at its default threshold (Journal of Clinical Sleep Medicine, 2026). Against the lab's oximeter, Galaxy Watch 4 blood oxygen showed a root-mean-square error of 2.54 percentage points in 51 adults (Journal of Clinical Sleep Medicine, 2024) and 2.3 percentage points with negligible bias in 97 adults with sleep disturbances, though 26.5 percent of readings were rejected, largely from changes in contact pressure (Sleep Health, 2022). Specificity in the 60s means a share of people flagged by the watch will not have moderate-to-severe apnea.

In 201 patients at a cardiology service, 31 percent of whom had atrial fibrillation, the Galaxy Watch 3 matched the Apple Watch 6 at 85 percent sensitivity and 75 percent specificity against a physician-read 12-lead ECG, with 17 percent of its tracings inconclusive. Manual review could read the rhythm on 99 percent of the single-lead tracings the algorithms could not classify (JACC: Clinical Electrophysiology, 2023).

Pixel Watch 3's VO2 max estimate was off by 0.53 mL/kg/min on average but individual readings ran from 12.56 below to 11.50 above the lab value, an 8.65 percent average error, and its calorie estimate carried a 15.02 percent error with wide variation between people (PLOS One, 2026). Galaxy Watch 6 and 7 calorie estimates did not differ significantly from indirect calorimetry on average in 148 adults, with average errors of 10.10 to 12.55 percent (JMIR Formative Research, 2026), and Galaxy Watch 4 step counts were within 10.5 percent of a thigh-worn reference across a day, against 6.4 percent for Apple Watch 6 (Sensors, 2024).