Did Oura lie about the accuracy of their smart rings?

The Facts

Madison Surber says she encountered Oura advertising in April 2025 and bought an Oura Ring 4 Gold the following month. The complaint lists a purchase price of approximately $513.68 and says she relied on representations that the ring could accurately track sleep stage by stage.

After wearing it as directed, Surber alleges, the device failed to track the hours she slept, when she awoke and the quality of her sleep. She says she wouldn’t have bought the ring had she known what the complaint describes as its sensor limitations.

Her proposed lawsuit covers Oura Ring 5, Oura Ring 4 and Oura Ring 4 Ceramic products sold in the United States. It seeks to represent a nationwide class of purchasers and a California subclass covering purchases within four years before the complaint was filed. Those groups are only proposed; the court has not certified either class.

These percentages shouldn’t be treated as automatically interchangeable. The complaint doesn’t provide the complete methodology needed to determine whether each figure used the same algorithm, population, product generation or statistical definition of accuracy. That comparability is one of the case’s unresolved technical questions.

What Oura Marketed

The complaint collects statements from Oura websites, product pages and technical articles that describe the rings as accurate and capable of delivering detailed sleep-stage analysis. Among them are “Built for accuracy,” “Unparalleled Accuracy” and a claim of “95% Sleep Staging Accuracy Compared to clinical sleep lab.”

Another Oura statement reproduced in the filing claims “79% agreement with gold-standard polysomnography” when classifying wake, light, deep and rapid eye movement, or REM, sleep. The complaint argues that these statements collectively communicate clinical-grade reliability to an ordinary buyer, even if individual claims use somewhat different language.

The filing also describes a broad advertising operation spanning Oura’s own site, retail pages, Facebook, Instagram, TikTok, YouTube and other platforms. It alleges that dynamic advertising tools allowed Oura to recombine promotional elements and retarget consumers. That may help explain the claimed reach of the message, but it doesn’t by itself prove that the message was false.

How Sleep Staging Works

A clinical sleep study is called polysomnography, usually shortened to PSG. It records several signals at once. Electroencephalography, or EEG, captures electrical brain activity. Electrooculography, or EOG, records eye movement. Electromyography, or EMG, measures muscle activity. Those signals help specialists classify sleep into wakefulness, REM sleep and non-REM stages.

Oura’s ring doesn’t contain scalp electrodes, eye leads or chin sensors. According to the complaint, it instead feeds heart rate, heart-rate variability, movement, skin temperature and, in newer models, blood-oxygen trends into a machine-learning algorithm. The result is an estimate of sleep stage based on patterns that correlate with sleep, rather than a direct recording of the neurological activity used to define the stages clinically.

The distinction between direct measurement and inference is real. It isn’t, by itself, proof that an estimate has no value. The decisive questions are how well the estimate performs, whether performance changes across users and whether Oura described those limitations clearly enough at the point of sale.

The complaint’s strongest issue is not merely that the ring lacks an EEG. It is whether Oura attached clinical-sounding certainty to estimates whose accuracy and limitations were more complicated than the advertising conveyed.

The Evidence Behind the Accuracy Dispute

The complaint cites a 2025 study published in Scientific Reports, a Nature Portfolio journal, involving 45 patients over 45 nights. As summarized in the filing, the Oura ring underestimated light sleep by 13.84 minutes and deep sleep by 5.98 minutes while overestimating REM sleep by 31.56 minutes. The complaint reports an overall sleep-stage accuracy of 53.18%.

A second cited study from University of Massachusetts researchers allegedly found significant differences between Oura and PSG in both younger and older adults, with lower accuracy among older adults. The complaint doesn’t provide a single overall accuracy figure from that study.

The filing also cites an Oura-funded validation study. According to the complaint, that research found systematic overestimation or underestimation at certain amounts of light and deep sleep. Surber’s lawyers present those results as evidence that Oura knew its performance depended on how much time a wearer spent in each stage.

The court would need more than a row of percentages. Expert evidence would have to explain the accuracy metric, product generation, algorithm version, population, testing conditions and whether Oura’s wording conveyed the study results fairly to a reasonable buyer.

Who Was Affected—and What Is Actually Documented

Surber alleges a direct economic consequence: she paid more than $500 for a product she says she wouldn’t otherwise have bought. She claims the sleep data did not track her experience and that she derived no benefit from the ring’s use. Those assertions have not been tested in court.

The proposed class theory extends that claimed overpayment to other U.S. purchasers. The complaint says tens of thousands of buyers, possibly more, may fall within the nationwide class. That is an estimate in a pleading, not a certified class size or a judicially established number of injured consumers.

The filing cites an American Academy of Sleep Medicine survey reporting that 68% of sleep-tracker users changed their behavior after learning more about their sleep. That finding helps explain why accuracy can matter in ordinary life: people may act on the numbers they see each morning. It does not establish that Oura data caused a particular buyer to make a harmful decision.

No physical injury, diagnosed sleep disorder or specific adverse health outcome is established by the supplied record. The concrete harm alleged here is principally financial, accompanied by Surber’s claimed inability to rely on the product’s advertising and sleep-stage results.

What Oura Knew Is Alleged, Not Established

The complaint alleges that Oura knew its marketing was misleading because the company employs an in-house scientific team, understood how PSG works, published validation research and acknowledged the difference between its ring and a clinical study.

Surber’s lawyers cast that statement as a contradiction of the more prominent accuracy claims. Oura could argue that comparison with PSG is a validation method rather than a claim that the ring contains the same sensors. The supplied source includes no Oura answer, so its legal and scientific position on that issue isn’t available here.

The complaint also points to Oura’s claim that more than 25 PhDs work across its interdisciplinary science team. From that expertise, the plaintiff infers knowledge of the difference between direct neurological measurement and algorithmic estimation. The complaint does not include an internal email, testimony or company document saying executives believed a particular advertisement was false.

The Legal Fight

Surber asserts seven causes of action, including fraud by misrepresentation, unjust enrichment, violations of three California consumer-protection statutes and breaches of express and implied warranties. She seeks damages, restitution, disgorgement, possible punitive damages and an injunction changing how Oura advertises or sells the products.

The complaint says more than $5 million is in controversy, a jurisdictional allegation used to place the proposed class action in federal court. It is not a damages award or a court finding that consumers lost that amount.

To prevail, the plaintiff would need to establish more than imperfect readings. Among other issues, she would have to prove that the challenged statements were false or misleading in context, that they were material to purchasing decisions and that recoverable losses can be shown under the asserted laws. Class certification would add separate questions about whether purchasers saw sufficiently similar representations and can be treated as a group.

What the Court Has Actually Decided

Nothing in the supplied record shows a merits decision. The document is the opening complaint.

No judge has found that Oura’s sleep-stage estimates are inaccurate, that the company deceived consumers, that Oura knew an advertisement was false or that Surber and other purchasers are entitled to compensation. The court also has not certified the proposed nationwide class or California subclass.

Similarly, the source contains no dismissal order, settlement, trial verdict or regulatory finding. The scientific studies cited in the complaint may become evidence, but their legal significance and comparability to Oura’s advertised figures remain unresolved.