Smart rings may look like a piece of jewelry, but do not judge a book by its cover. These tiny devices harbor advanced sensors and complex software that can monitor your heart rate, sleep quality and many other health stats you would typically track with your smartwatch. Smart rings are also light, discreet and arguably more stylish than chunky wrist-worn wearables. No wonder these innovative devices are making some serious waves in the tech industry.
Smart rings have been around for less than a decade, but they have already solidified their position among some of the best fitness trackers on the market, whether it is the best-selling Oura ring or the Ultrahuman AIR Ring. Industry giants like Samsung and Amazfit have already released their smart rings, and even Apple was rumored to follow the lead (that said, it is unlikely to happen anytime soon).
These tiny marvels of technology seem to have a bright future ahead of them. But how accurate are smart rings, and how do they compare to fitness watches? We asked the experts.
Smart rings are less functional — for now
Smart rings tend to have fewer tracking features than smartwatches. They can’t map out your running route, automatically detect your workouts or count your sets and reps while lifting weights, for example (that is because they do not tend to have advanced motion sensors or built-in GPS). In that sense, wrist-worn wearables are still a go-to choice for fitness enthusiasts and this is unlikely to change anytime soon.
However, smart rings are yet to reach their full potential, and we really need to emphasize that before we begin our deep dive into the topic.
Dr. Robert Sackin, a patent attorney and an engineer with extensive experience in healthcare technology, told Live Science that smart rings are evolving rapidly. “This is evidenced, for example, by the massive increase in patent applications filed in relation to the Oura Ring. The first-generation Oura Ring was launched in 2015 on the back of a Kickstarter campaign. For the last complete calendar year [2024], there were 88 US patent applications published for the Oura Ring,” Sackin said.
Scientists are continuously improving tracking sensors and developing new biometric technologies, so in the not-so-distant future, commercially available smart rings could be capable of tracking health stats like blood glucose levels, hydration status and blood pressure.
“If these parameters can be tracked accurately, we may see increased use in medical applications, particularly in the early detection of various health issues, including heart disease and diabetes,” Sackin said.
Exercise enthusiasts will not be left empty-handed, either. “From a fitness perspective, future smart rings could integrate seamlessly with other fitness apps and healthcare systems, providing users with a more holistic view of their health and making it easier to share data with healthcare providers or personal trainers,” Sackin said.
Moreover, the next generation of smart rings could in fact be far more functional than fitness watches, all thanks to the fact that they are placed on the finger instead of the wrist.
For example, scientists have developed a smart ring that can monitor hand hygiene in real time. This innovative device has an electrochemical fluid sensor that can detect when you wash your hands, and how long for. In the preliminary tests, this prototype has shown 97.8% accuracy, which is 10.2%–15.9% higher than electronic monitoring systems used in healthcare facilities, according to a study published Jan. 2024 in the journal IEEE Transactions on Mobile Computing.
Scientists are also working on a smart ring that can help detect hand tremors, according to a 2021 study published in the journal Computer Modeling in Engineering & Sciences. Hand tremors are one of the key symptoms of Parkinson’s disease, a neurodegenerative disease that affects mostly the elderly, and their early detection could be vital for the management of this condition, the study authors noted.
So, when we discuss the accuracy and capabilities of smart rings, it is important to reiterate that these devices are constantly evolving. With that in mind, let’s dive into the science behind smart rings.
Smart rings and heart rate measurements
Smart rings detect heart rate in the same way that smartwatches do — by using photoplethysmography (PPG). This technology uses optical sensors that emit light at specific wavelengths into the skin, and photodetectors that measure how much of that light is reflected back to the tracker. Since blood is better at absorbing that light than other bodily tissues, fitness trackers can detect when the blood volume in your vessels increases and decreases. The rhythmic changes in blood volume are what they interpret as heartbeats.
However, this technology is not without its flaws. For PPG to work properly, optical sensors need to be positioned close to blood vessels. Otherwise, they may not be able to accurately measure the heart rate.
This is where smart rings may have a competitive edge over smartwatches. According to a 2022 review published in the journal Frontiers in Physiology, fingers produce more accurate heart rate measurements than wrists, simply because they have a more robust network of blood vessels that are located closer to the skin.
Preliminary evidence also suggests that smart rings may produce more accurate PPG measurements in people with darker skin tones, according to a 2023 study published in the journal Mayo Clinic Proceedings: Digital Health. One of the major drawbacks of this technology is that melanin, a dark pigment in the skin, can absorb some of the light emitted by optical sensors and therefore distort heart rate measurements. However, there is generally less melanin on the palm than on the wrist, researchers noted.
That said, smart rings can still produce inaccurate readings and should not be treated as medical tools, Dr. Bhaskar Semitha, a cardiologist and cardiothoracic surgeon at Fortis Hospital Vashi in Mumbai, India, told Live Science by email. “They cannot detect arrhythmias as accurately as an ECG, and they certainly cannot predict a heart attack. I have had patients panic over false alarms from their wearables, and I have also had patients ignore real symptoms because their smart ring data looked normal. That is where these devices can be misleading,” Semitha said.
There are many reasons why that is the case. Just like fitness watches, smart rings may not record heart rate properly if the device is not fitted tightly enough or the skin temperature is too cold (blood vessels tend to narrow in low temperatures.) Motion artifacts, which are disruptions to the PPG signal caused by rapid movements, are another factor that can significantly affect the accuracy of optical sensors. One 2021 study published in the Journal of Electrical Bioimpedance found that smart rings can be prone to motion artifacts even during relatively mild exercise.
Indeed, smart rings tend to be most accurate during rest, Semitha said. “A ring has a much smaller contact area [than a fitness watch]. If it shifts even slightly or if the wearer’s hands are cold, the readings can be off. When someone is exercising, the accuracy drops even more. If the wearer is gripping a weight or moving their hands a lot, the numbers can be unreliable,” he explained.
Wrist-worn wearables are better suited for workout tracking than smart rings, Sackin agreed. “Fitness watches, especially those designed with advanced features (like the Apple Watch or some Garmin watches), often have more sensors than smart rings and are better equipped to capture heart rate data accurately during exercise. Moreover, fitness watches tend to stay in close proximity to the wrist, making it easier to capture a consistent reading during moderate physical activities,” Sackin said.
Smart rings and sleep tracking
Smart rings are often used for sleep tracking, and for a good reason. “They are lightweight and comfortable, so people are more likely to wear them overnight. This allows for continuous monitoring without interruption,” Semitha said. However, smart rings may not be too reliable when it comes to certain aspects of sleep tracking, according to a 2024 meta-analysis published in the journal Applied Sciences.
Scientists compiled data from 19 research studies and found that smart rings vary in their estimations of total sleep time and often underestimate the duration of the REM phase, a crucial stage of sleep characterized by increased brain activity and vivid dreams. That is because, just like most fitness watches, many smart rings assess what sleep stage you are in based on your heart rate and movement, and these are only indirect signs of sleep quality, Semitha explained. “Smart rings are useful for spotting patterns, but they are not a substitute for a real sleep study that measures brain activity,” he said.
However, some smart rings may still be better at assessing sleep than the vast majority of fitness watches available on the market, Sackin said. “The Oura Ring, for example, combines motion tracking, heart rate data, body temperature and respiratory rate to estimate sleep stages, and it is specifically designed with sleep in mind,” Sackin said. Fitness watches, on the other hand, tend to be geared more towards exercise performance.
The bottom line
So, in the smart ring vs smartwatch debate, which fitness tracker wins for accuracy and functionality? It is a tough question to answer. Both wearables come with pros and cons, and depending on how and when you intend to use them, both can make a tangible difference to your lifestyle goals. Plus, neither smart rings nor smartwatches boast 100% accuracy. That said, these discreet fitness trackers can still help you spot patterns in your heart rate and sleep measurements.
“For now, smart rings should be seen as helpful tools for tracking trends, not a replacement for real medical assessments. However, I believe they will become more accurate over time,” Semitha concluded. “They are constantly evolving, and the idea of continuous, passive health monitoring is surely exciting.”
This article is for informational purposes only and is not meant to offer medical advice.
