Smart ring maker Oura faces a proposed class-action lawsuit alleging it misled consumers regarding the accuracy of its sleep-stage and sleep-quality measurements.

The complaint was filed Thursday in the U.S. District Court for the Northern District of California. Plaintiff Madison Surber claims she purchased an Oura Ring 4 for about $513.68 in May 2025 after seeing marketing claims about the device's capabilities.

The Allegations

Surber argues that Oura promoted its rings as capable of accurately measuring sleep stages despite not containing the same types of sensors used in clinical sleep studies. The complaint alleges the company advertised sleep-stage accuracy figures of 79% and 95%.

The lawsuit contends these representations are misleading because the device lacks sensors used in polysomnography (PSG), widely considered the clinical reference for measuring sleep. Surber argues that consumers are given the impression the ring provides measurements comparable to clinical equipment.

"No consumer would understand Oura’s promises of unparalleled accuracy to equate to the reality: a coin flip’s chance of being correct," the lawsuit reads. The complaint also alleges that Oura's AI models make guesses based on "improper inputs" and present AI-based inferences as reliable science.

Oura’s Defense

Oura disputed the allegations, defending its research and accuracy claims. A spokesperson stated the company stands behind its science, noting that the ring estimates sleep stages using multiple physiological signals including heart rate, heart rate variability, movement, breathing patterns, and temperature.

Oura pointed to peer-reviewed research supporting the use of physiological signals to classify sleep stages. The company said its sleep staging has been validated against polysomnography, which it described as the gold standard for sleep measurement.

While acknowledging the ring is not a medical device or a substitute for a clinical sleep study, Oura stated its sleep staging has been validated and compared favorably in multiple studies against PSG. The company noted that more than 1,200 nights of data were collected to inform the development of its sleep-staging algorithm, known as NSSA.

Legal Claims

Attorneys for Surber say they identified numerous advertisements and product pages containing the challenged representations. They argue the products lack the sensors required to directly measure the neurological activities that clinically define sleep stages.

The case brings seven causes of action, including alleged fraud by misrepresentation, unjust enrichment, violations of California’s Unfair Competition Law, False Advertising Law, and Consumers Legal Remedies Act, as well as alleged breaches of express and implied warranties.

Surber is seeking damages and other relief, including an injunction that would require Oura to stop making the allegedly misleading representations. Oura stated it will defend against the allegations in the appropriate legal forum.