Oura is the most popular smart ring maker, with revenue in the range of $1 billion. (Image credit: Oura)Oura, the popular Finnish company best known for its sleek smart ring that tracks health, fitness, and sleep, has been accused of falsely advertising its ability to accurately measure sleep quality and sleep stages.The proposed lawsuit, filed last week by the Clarkson Law Firm in San Francisco, alleges that Oura marketed its rings as “built for accuracy” and capable of providing “unparalleled accuracy” in tracking sleep stages—wake, light, deep, and REM sleep. However, the rings lack the sensors needed to directly measure the brain activity and eye movements that define those stages.According to the lawsuit, the sleep-tracking claims made by the company are inaccurate because the ring’s hardware is not capable of accurately identifying sleep stages, which requires equipment such as scalp electrodes and eye sensors used in clinical polysomnography, the gold-standard sleep study conducted in hospitals and laboratories.“To capitalize on consumers’ desire for a tracker that could actually track sleep and monitor their sleep cycles, Oura sold expensive tracking rings, priced at $300 and up, advertising exactly that: that Oura rings are capable of seeing what only a hospital sleep lab can see, including the four different stages of sleep,” the complaint reads. “Oura did not just claim to measure a heartbeat or a temperature, but the exact stage of sleep the wearer is in—which in reality requires electrodes in the scalp and sensors on the eyes, as only a hospital or other clinical setting can do.”Also read | From stress peaks to sleep efficiency: How a fortnight of biometric data revealed my real fitness baselineIt says the company has claimed “79%” accuracy in sleep-stage tracking and, more recently, “95% Sleep Staging Accuracy compared to clinical sleep lab.”Attorneys brought the suit on behalf of Madison Surber, a Californian who purchased an Oura Ring for $513.68 in 2025 based on the disputed marketing claims.“Sleep happens in the brain, not on one’s finger,” the complaint states.Story continues below this ad Oura’s smart ring has evolved beyond sleep tracking to offer a broader range of health and wellness features. (Image credit: Nandagopal Rajan/Indian Express)Oura disputes the allegations.“We dispute the allegations in this complaint and intend to defend against them,” a company spokesperson told USA Today.Oura said that while its ring is not “a substitute for a clinical sleep study,” its methodology “has been validated and compared favorably in multiple studies” against laboratory sleep studies.Also read | How screenless wearables like Whoop and Oura ring are making discreet fitness tracking popularLaunched in 2015, Oura has become the most successful smart ring maker, a segment that big tech companies have been unable to capitalize on despite their vast marketing budgets and R&D resources. Over the years, however, the market has gradually shifted toward health-focused wearables.Story continues below this adEarlier this year, Oura filed a draft of its IPO prospectus with the U.S. Securities and Exchange Commission. Last year, Oura announced that it had sold more than 5.5 million Oura Rings since the product’s launch, up from the 2.5 million rings the company said it had sold as of June 2024.