A smart ring's purchase price is not its price. Oura's published membership terms put the running cost at $5.99 USD/month or $69.99 USD/year, and Oura's member care page on membership states that without a membership the ring and app still function but the insights and personal health data are much more limited, with one included month for new members. Three years of the annual plan is $209.97 on top of the hardware. The condition that changes the hardware side is finger size: the manufacturer publishes battery life, weight and thickness as ranges across its size run, so the figure that applies to you depends on which size the sizing kit lands on.
Oura publishes the hardware as ranges, not single numbers
Every figure a ring maker prints comes from its own bench, because no standards body defines a sleep score, a readiness score or a recovery index. Oura's Ring 4 specification page states battery life as typically 5 to 8 days and charging as typically between 20 and 80 minutes depending on the starting charge, sizes 4 to 15, a width of 0.31 in (7.9 mm), a thickness of about 0.11 in (2.88 mm) for the titanium Ring 4 and 0.14 in (3.51 mm) for the Ring 4 Ceramic, a weight of 0.12 to 0.18 oz (3.3 to 5.2 grams) for the titanium version and 0.18 to 0.29 oz (5.1 to 8.1 grams) for the ceramic, water resistance to 328 ft (100 m) described as suitable for sauna and water sports but not diving, and an operating temperature range of 14 to 129 °F (−10 to 54 °C).
The sensor list on that same page names what each part measures: red and infrared LEDs for blood oxygen during sleep, green and infrared photoplethysmography sensors that alternate to measure heart rate around the clock and heart rate variability and respiration rate during sleep, a digital temperature sensor for average body temperature variations, and an accelerometer for movement and activity. That is a list of signals, not of diagnoses, and the manufacturer's wording keeps it there. Overnight temperature and heart-rate trends are also the numbers people reach for when judging a mattress, and they carry the same caveat.
Run the manufacturer's own range against a charging habit. At the low end of Oura's stated 5-to-8-day battery, a ring needs charging roughly 73 times a year; at the high end, about 46. A charge that takes up to 80 minutes has to come out of waking hours, because a ring on a charger is not measuring the night it was bought to measure. A watch has the same problem on a shorter cycle, which is why smartwatch specifications quote fast-charge figures in minutes.
The FDA names smart rings in its blood pressure notice
The health claims a wearable is permitted to make are set outside the product page. In its safety communication of September 16, 2025, the FDA told consumers not to use unauthorized blood pressure devices, including software features on wearables such as smartwatches and smart rings that claim to measure blood pressure, regardless of brand, and pointed them to the FDA's 510(k) database to check whether a given device is authorized.
The broader line sits in the agency's guidance. The FDA's General Wellness: Policy for Low Risk Devices, issued January 6, 2026, defines general wellness products as those intended only for general wellness use and presenting a low risk, and states that the Center for Devices and Radiological Health does not intend to examine such products for device status or for premarket review, registration and listing, labeling, manufacturing practice or Medical Device Reporting requirements. That guidance also draws the boundary: products are not general wellness products when they are intended to measure, estimate or report physiologic values for medical or clinical purposes, including screening, diagnosis, monitoring, alerting or management of a disease or condition, and it names electrocardiogram recording and analysis devices and blood pressure monitors among the examples. A ring sold under the wellness policy has not been reviewed for accuracy by anyone outside the company that built it.
Before you buy a smart ring
- The membership price per year and the multi-year total: at Oura's published $69.99 a year, three years is $209.97 beyond the hardware.
- Which specific scores and reports stop appearing if the membership lapses, in writing, before the included month ends; a video doorbell subscription is priced the same way.
- The battery figure for your size rather than the range, and the charge time in minutes, since charging happens during waking hours.
- The sizing kit policy: what it costs, how long it takes, and whether a resize after purchase is free.
- Whether a health feature is FDA-cleared or sold under the general wellness policy, which decides whether anyone outside the manufacturer reviewed it.
- The data export format and whether history downloads in a usable file if the membership ends.
- The warranty length and what it says about scratches, finish wear and a ring that no longer fits, which are the three most common failures on a worn item.