Technology
25.05.2026
Sleep Tracking with a Smartwatch: What the Data Tells You
Deep sleep, REM and resting heart rate: tips for reading your smartwatch sleep report.
Smartwatches split sleep into stages by combining movement, heart rate and heart-rate variability data. The results are not as precise as a clinical sleep study, but they are very useful for spotting long-term trends.
Sleep stages
In adults, roughly 15–25% of the night is deep sleep and 20–25% is REM. One low night is nothing to worry about; look at the weekly average.
Resting heart rate and HRV
A higher-than-usual resting heart rate can signal a late dinner, alcohol or an oncoming illness. A drop in heart-rate variability (HRV) shows your body needs to recover.
- Wear the watch one finger above the wrist bone, slightly snug.
- Try to go to bed at the same time every night.
- Reduce screen brightness an hour before bed.
