Oura Ring 4 is not only the most comfortable evolution of the revolutionary smart ring—it’s also the most accurate.
Powering this unparalleled accuracy is a breakthrough sensing platform unique to Oura Ring 4, Smart Sensing. Smart Sensing allows Oura Ring 4 to adjust to your unique physiology and lifestyle—providing a precise and continuous picture of your overall health, while also optimizing battery usage.*
How Smart Sensing Works
The most meaningful data starts with the most personalized measurements.
Smart Sensing is powered by an algorithm that works alongside the research-grade sensors within Oura Ring 4 to respond to each member’s unique finger physiology, including the structure and distinct features of your finger (i.e. skin tone, BMI, and age).
The multiple sensors form an 18-path multi-wavelength photoplethysmography (PPG) subsystem, which adjusts dynamically to your lifestyle throughout the day and night.
The sensors in Oura Ring 4 include:
- Red and infrared LEDs, which measure blood oxygen levels while you sleep
- Green and infrared LEDs, which alternate to measure heart rate and heart rate variability 24/7 and respiration rate as you sleep
- A digital temperature sensor, which measures your skin temperature variations
- An accelerometer, which tracks movement and activity
The PPG sensors are placed asymmetrically within Oura Ring 4, providing a variety of distances and tissue penetration depths for measurements. As finger vasculature differs between people, the different measurement locations around the inner surface of Oura Ring 4 help achieve the best possible power efficiency and signal quality.
Combined with high-fidelity motion detection and calibrated peripheral temperature sensing, these sensors enable precise measurement of the 30+ health and wellness metrics that Oura tracks, including:
- Heart rate
- Heart rate variability
- Bedtime detection
- Sleep staging
- Blood oxygen levels (SpO2)
- Cardiovascular Age
- Cardio Capacity (VO2 Max)
- Daytime Stress and Resilience
- Body clock and chronotype
- Cycle Insights
- Automatic Activity Detection plus heart rate zones
- And much more
Improved Battery Life
Smart Sensing also helps maximize the battery life of Oura Ring 4 by dynamically adjusting the brightness of the LEDs, using the dimmest possible setting to achieve the desired signal quality. This allows the battery life of Oura Ring 4 to extend up to eight days.*
Research-backed Accuracy
Oura prioritizes accuracy in everything we do, from our sleep staging algorithm to blood oxygen sensing. Thanks to Smart Sensing, Oura Ring 4 is the most accurate iteration of Oura Ring yet.
To determine exactly how much better, Oura conducted an external research study in August 2024 where 60 participants wore both Oura Ring Gen3 and Oura Ring 4 overnight in a sleep clinic.
In addition to the two smart rings, each participant also wore an array of reference devices, including a heart monitor and a brain activity monitor. These sensors, when interpreted by an expert, are used to establish a polysomnogram—the gold standard measurement of sleep physiology. A polysomnogram measures information such as sleep stages, heart activity, breathing rate, and blood oxygenation levels.
With this rich dataset, Oura scientists were able to precisely establish the accuracy of Smart Sensing, both by comparing it to Oura Ring Gen3 and to the gold standard recordings obtained in the lab. The findings include:
- 120% improvement in signal quality (1) for blood oxygen sensing (SpO2), translating to a 30% increase in accuracy in average overnight SpO2 measurement (2)
- 15% more accurate breathing disturbance index (BDI) thanks to the higher signal fidelity (3)
- 7% fewer gaps in the daytime heart rate graph (4)
- 31% fewer gaps in the nighttime heart rate graph (5)
While these results highlight the average performance across all study participants, individual experience may deviate from these numbers. Generally, the study showed that the biggest improvements could be expected in the most challenging cases, leading to more consistent Oura Ring performance across a wider range of fingers.
*All battery claims depend on Oura Ring size, Oura App settings, feature configuration, activity, age of battery, usage, and many other factors; actual results will vary. Battery life and charge cycles vary by use and settings. Battery tests were conducted across various sizes and scenarios. See Ring Battery tips for more information.
(1) We compare the perfusion index signal quality metric between the selected OR4 SpO2 channels and to the Gen3 SpO2 channels
(2) SpO2 accuracy is defined as the percentage of nights where the mean SpO2 value is within 2 points of the reference value
(3) BDI accuracy is based on comparison against human-annotated SpO2 desaturation events
(4) Gaps are defined as 15 minute segments with missing heart rate data
(5) Gaps are defined as 5 minute segments with missing heart rate data