Every morning your watch or ring gives you a score out of 100 and a verdict on your body. Some of that number is measurement. Some is an estimate. Some is a private formula nobody has ever shown you. This 17-page guide shows you which is which.

INSIDE

• The accuracy scoreboard: what your device measures well, estimates roughly, and models entirely
• Why steps and resting heart rate are worth trusting, and sleep stages and calorie counts are not
• The 5 numbers with real evidence behind them, and what to do with each one
• 6 rules for reading any metric, and what counts as a real change
• A 14-day method that turns your data into one clear decision instead of a daily verdict
• Which alerts matter, and which symptoms need a doctor whatever your score says
• How to use the device without it using you: weekly reviews, notifications off
• Setup checklist, baseline worksheet and a printable 5-minute weekly review

Works with any tracker: Apple Watch, Oura, Fitbit, Garmin, Whoop, Samsung or a budget band. No brand is recommended and nothing here is sponsored.

Based on published research, including device validation against clinical sleep testing and ECG. Every source is listed on the last page.

Instant PDF download. General wellness information, not medical advice. Wearables are not diagnostic devices.