Performance & Accuracy
Smart Sensing: The 18‑path optical array dynamically selects the clearest signal, trimming motion noise by ~25 % versus Gen 3. Early lab validation pegs sleep‑stage agreement at 93 % against polysomnography—an industry high.
HR & HRV: Continuous daytime HR adds green‑LED channels for ±1 bpm error. Night‑time RMSSD stays within ±1.5 ms of ECG in controlled trials.
Health Features
- Daytime Stress 2.0: Minute‑level HRV + temp combine with movement tags to label micro‑stressors and suggest breathwork.
- Automatic Activity Detection (AAD): Now captures average HR and HR zones across 40+ sports without manual start/stop.
- Cycle Insights (β Fertile Window): Temp‑trend fertility predictions expanded for TTC users.
- Cardio Capacity: VO₂‑max estimation moves from Labs to main app with weekly trend arrows.
Comfort & Build
Recessed sensors sit 1 mm deeper than Gen 3, eliminating the pressure “ridge.” Fully titanium inner shell resists sweat acidity, and the outer DLC variant shrugs off micro‑scratches better than before.
Battery Life
In mixed use (24/7 HR, AAD, SpO₂ ON) we averaged 6.4 days; disable daytime HR broadcast and you’ll push 8 days. The new dock hits 40 % in 22 minutes—enough for a long weekend.
App Experience & Membership
The app’s three‑tab overhaul (Today, Vitals, My Health) surfaces trends faster, but the paywall remains: without membership you see only charge level, RHR, and temp deviation.
Pros & Cons
| Pros | Cons |
|---|---|
| Smart Sensing boosts accuracy & motion tolerance | Membership still mandatory for full data |
| Up to 8‑day battery, USB‑C fast charging | No on‑ring display or notifications |
| Sleeker, lighter, recessed sensor design | Still no NFC/contactless payments |
| Expanded sizes 4–15 & six durable finishes | Only one style (no flat Heritage option) |
Final Verdict
If you value precision recovery and stress insights in a form factor you forget you’re wearing, Oura Ring 4 is the new class leader. For step‑count obsessives or anyone turned off by subscriptions, competing rings with on‑ring displays (or a discounted Gen 3) may satisfy at lower cost.