4 sleep trackers tested 90 nights vs polysomnography reference. Real accuracy data.
Devices
- Apple Watch Series 9 ($399 iOS only)
- Oura Ring Gen 4 ($349 + $5.99/mo)
- Whoop 4.0 ($30/mo)
- Fitbit Charge 6 ($159)
Sleep Stage Accuracy (vs PSG)
Light sleep: Apple 91% · Oura 88% · Whoop 86% · Fitbit 82%
Deep sleep: Apple 87% · Oura 85% · Whoop 89% · Fitbit 79%
REM sleep: Apple 92% · Oura 89% · Whoop 84% · Fitbit 81%
Verdict by use case
iOS daily: Apple Watch S9. Recovery + HRV: Whoop 4.0. Sleep ring: Oura. Budget: Fitbit Charge 6.
Most actionable metrics
Sleep latency · total sleep time · wake events. Sleep efficiency >85% is the key metric.
Not a substitute for licensed sleep medicine physician. Symptoms >3 weeks · consult specialist.
Complete: V8 28-Day Sleep Audit + Mattress Bundle ($24.99 saves 37%).
AI-assisted research synthesis · human-edited by SUJI KIM · EU AI Act Art. 50 transparency
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By SUJI KIM · 30-day refund Gumroad standard