Oura Ring 5 Scientific Test (Initial Review)
In a Nutshell
Oura Ring 5 delivers excellent nighttime heart rate and HRV accuracy within 1-2 BPM of ECG chest straps, plus strong 94% deep sleep detection against EEG reference, but scores only 84.1 for exercise heart rate tracking—ranking "meh" overall and unsuitable as a primary workout monitor. Outdoor cycling performed worst (0.74 correlation) due to grip interference, while running was strong (0.94-0.95). The smaller form factor offers no meaningful performance gains over Ring 4, making upgrades unnecessary for current owners unless size reduction is specifically desired.
These notes were generated by AI and may contain inaccuracies.
Competition is increasing in the wearable market with the Fitbit Air launch competing against the Whoop strap, and various smart rings entering the market to compete with the Oura ring. The Oura Ring 5 was launched with the main selling feature being that it's smaller than the previous generation. However, this smaller form factor required fitting a battery and sensor set into a reduced size, which led to a smaller sensor set inside the new Oura Ring 5 compared to the Oura Ring 4.
The reviewer does not particularly value the smaller size, preferring the larger size of the Oura Ring 4. The purpose of this initial scientific test is to evaluate what the Oura Ring 5 does well and identify its limitations, particularly whether the reduced size has compromised performance.
The testing involves comparing the Oura Ring 5 against reference devices during sleep. An ECG chest strap was worn alongside the Oura Ring 5 for several nights to measure heart rate and heart rate variability. The data was extracted and similarity calculated between the two measurements.
Multiple nights showed good agreement between the Oura Ring 5 and ECG chest strap measurements. The heart rate readings were typically within 1-2 BPM of each other. One night showed some deviation where the reference device recorded higher heart rates, but overall the measurements were consistent. The heart rate range tested was narrow, typically between 42-49 BPM, requiring the device to measure small differences accurately.
The correlation between the reference ECG measurements and the Oura Ring 5 heart rate was very high, with data points closely aligned to the perfect agreement line. The reviewer wore the ring on their ring finger during testing, noting they have another ring on the way for index finger testing.
Heart rate variability measurements during sleep also showed excellent agreement with the ECG reference. Multiple nights demonstrated strong correlation between the Oura Ring 5 and the reference device. The data points aligned closely to the perfect agreement line, indicating the device performs well for both heart rate and heart rate variability tracking during nighttime.
The Oura Ring 5 was tested during indoor cycling (spinning) against a Polar H10 chest strap reference. The correlation value was 0.85, which positioned the device near the lower end of performers tested in the past year. Individual spinning sessions showed mixed results - some sessions had good agreement while others showed the device struggling to detect heart rate changes, maintaining steady readings when changes should have been detected.
Running tests showed more promising results with a correlation of 0.94-0.95. Individual runs demonstrated good tracking in most cases, though one instance showed potential cadence lock issues where the device initially tracked running frequency rather than heart rate before correcting. The performance appears potentially better than the Oura Ring 4, though more testing is needed.
Outdoor cycling presented the greatest challenges with a correlation of only 0.74. The device struggled to track heart rate changes during activities involving handlebar grip, likely due to tension and pressure on the finger affecting sensor readings. Individual sessions showed the device missing peaks and dips in heart rate, only capturing median values. The performance was similar to the Oura Ring 4.
Using a new scoring scheme for heart rate tracking during exercise, the Oura Ring 5 received an overall score of 84.1, placing it in the "meh" category. The reviewer does not recommend it as a primary heart rate tracker during exercise, though it performs well for nighttime measurements.
Sleep stage tracking was tested against the ZMax EEG headband reference device, which measures brain waves for accurate sleep stage detection. Limited data was available due to reference device issues (battery swelling and charging port failure), but two good nights of data were collected for comparison.
The Oura Ring 5 showed 94% agreement for deep sleep detection compared to the EEG reference. Light sleep agreement was approximately 70%, and REM sleep agreement was also around 70%. While not perfect, these results were considered very good compared to competition. Individual night comparisons showed generally good alignment between the reference and Oura Ring 5 sleep stage detection.
When compared to other devices using average sensitivity across sleep stages, the Oura Ring 5 ranked among the top performers alongside the Oura Ring 4. The top five sleep stage tracking brands identified were: Oura Ring (both generations), Google/Fitbit devices including the Fitbit Air and Pixel Watch, Whoop Strap, Apple Watch, and Eight Sleep Pod.
The Oura Ring 5 received a sleep score of 78, placing it in the "great sleep stage tracking" category. The reviewer notes that if someone already owns the Oura Ring 4 and is satisfied with it, there may be no compelling reason to upgrade, as the core functionalities appear similar between generations.
Side-by-side comparison of size 8 Oura Ring 5 and Oura Ring 4 shows the Generation 5 is significantly smaller. The reviewer personally prefers the larger size of the Generation 4, though acknowledges this is subjective preference. Both sizes provide similar wearing comfort for the reviewer, though smaller rings might initially feel more comfortable for those not accustomed to wearing rings.
For new users interested in nighttime metrics, the Oura Ring 5 is recommended as a strong choice. Existing Oura Ring 4 owners are advised that the upgrade may not be necessary unless the smaller size is specifically desired. The reviewer plans additional detailed testing with more data to provide a comprehensive review.
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