A proposed class-action lawsuit against smart ring maker Oura alleges the company misled consumers about the accuracy of its devices’ sleep-stage and sleep-quality measurements.

The complaint was filed Thursday in the U.S. District Court for the Northern District of California and alleges Oura promoted its rings as capable of accurately measuring sleep stages despite not containing the same types of sensors used in clinical sleep studies.

Plaintiff Madison Surber claims she purchased an Oura Ring 4 for about $513.68 in May 2025 after seeing Oura’s marketing claims about the device’s sleep-tracking capabilities. According to the complaint, Oura has advertised sleep-stage accuracy figures of 79% and 95%.

Surber argues those representations are misleading because the Oura Ring does not contain the sensors used in polysomnography, or PSG, which is widely used as a clinical reference for measuring sleep.

The complaint alleges Oura’s marketing gives consumers the impression that the ring can provide sleep-stage measurements comparable to those produced by clinical equipment, despite differences in the underlying technology and testing methods.

"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 are making guesses based on what it calls "improper inputs," and accuses the company of presenting AI-based inferences as reliable science.

Oura disputed the allegations and defended its research and accuracy claims.

"We stand behind our science, research, and accuracy claims," an Oura spokesperson told Benzinga in a statement. The company said its 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 and said its sleep staging has been validated against polysomnography, which it described as the gold standard for sleep measurement.

"While Oura Ring is not a medical device or a substitute for a clinical sleep study, Oura’s sleep staging has been validated and compared favorably in multiple studies against polysomnography, the gold standard," the spokesperson said.

Oura also said more than 1,200 nights of data were collected to inform the development of its sleep-staging algorithm, known as NSSA, and pointed to a peer-reviewed paper describing how the algorithm was developed and how it uses signals collected by the ring. The company said multiple independent, third-party studies support its accuracy claims.

"We’re committed to continuing to clearly communicate what Oura measures, what it estimates, and how members should use that information," the spokesperson said. "We dispute the allegations and will defend against them in the appropriate legal forum."

Attorneys for Surber say they identified numerous Oura advertisements and product pages containing the challenged representations. 

"The Challenged Representations are there to reassure and promise consumers that this premium-priced wearable device will deliver clinical-grade insight into the user’s sleep patterns that a basic fitness tracker cannot. However, the Products lack the sensors that are required to directly measure the neurological activities that clinically define sleep stages," the complaint reads.

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.

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