Sleep Tracking Accuracy Guide Blog

Apple Watch and WearOS devices merge accelerometer data with optical heart sensors to detect sleep. Mark bed and wake times, let sleep mode trigger automatically, and keep the watch snug on the wrist to improve accuracy.

When reading reports, focus on total duration, number of awakenings, and average heart rate; REM and deep sleep minutes differ by algorithm. Export weekly trends to Apple Health or Google Health Connect to compare across apps.