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.

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