Smart rings do much of what a fitness tracker does, from a ring on your finger instead of a band on your wrist. In the UK the main names are Oura, Samsung's Galaxy Ring, Ultrahuman and RingConn, and they differ most in the details that matter after the box is open: sizing, battery life, which phones they pair with and whether the full app needs a membership. This guide takes each point from the makers' own product, sizing and support pages.
On an iPhone or Android phone, start with Oura's sizing kit for the Oura Ring 5, knowing Oura says most of its app needs an active membership after a free first month. Android owners can pick the Galaxy Ring, which Samsung says needs Android 11 or later. To skip a subscription, Ultrahuman and RingConn say their rings need none, and RingConn lists up to 14 days of battery for the Gen 3.
Key Takeaways
- Oura, Samsung, Ultrahuman and RingConn all list sleep, heart rate, skin temperature and activity tracking, and each says in its own words that its ring is for wellness, not medical diagnosis.
- Every maker says its ring sizes can differ from standard ring sizes, and Oura's sizing article lists sizes 6 to 13 for the Oura Ring 5 and sizes 4 to 15 for the Ring 4.
- Samsung UK says the Galaxy Ring must pair with an Android 11 phone and that its Galaxy Wearable app is not supported on iOS, while Oura, Ultrahuman and RingConn list both iPhone and Android.
- Oura's support article says that without an active membership the app shows only the Readiness, Activity and Sleep scores, while Ultrahuman and RingConn say their rings need no subscription.
- Battery claims run from 4 to 6 days for the Ultrahuman Ring AIR to 11 to 14 days for the RingConn Gen 3 with vibration off, and all four makers list a 100 metre water rating.
Smart Rings Track Sleep, Heart Rate, Temperature and Movement
Oura's product page for the Oura Ring 5 lists 24/7 heart rate, heart rate variability, sleep stages, blood oxygen and a digital sensor that measures temperature trends, and says Oura automatically detects over 40 activities. Heart rate variability, or HRV, is the small variation in time between heartbeats.
Samsung UK's Galaxy Ring page covers the same ground in its own words: movement and activity tracked without pressing a button, heart rate with alerts when it runs too high or too low, sleep stages, and skin temperature readings while you sleep. Ultrahuman's UK page says the Ring AIR tracks sleep, HRV, temperature and movement, and its buy page adds VO2 Max, steps and calories. RingConn's Gen 3 page lists 24/7 heart rate, HRV, blood oxygen, respiratory rate, skin temperature, stress and steps, plus sleep apnea risk indicators and vascular load trends overnight.
The overlap is large, and all four put sleep at the centre of the pitch. The real differences sit in fit, battery, phone support and running costs.
A Smart Ring Is Not a Smartwatch or a Fitness Band
None of the four makers' spec pages lists a display, so every score, graph and sleep chart lives in the phone app. RingConn's Gen 3 adds a vibration motor, and RingConn's FAQ says it is used for health alerts and reminders, not for messages or alarms.
What a ring gives back is size and battery. Ultrahuman's UK page calls the Ring AIR 11x lighter than a typical smartwatch, and RingConn's own comparison chart puts smartwatches at 0.75 to 1.5 days of battery against 10 days for its Gen 2 Air. Those are the ring makers' comparisons, so read them as marketing rather than independent figures.
The choice comes down to what you want on your body. For notifications on the wrist or a screen to check during a run, a watch does more, and the smartwatch guide covers the Apple Watch, Galaxy Watch and Pixel Watch. For a screen at a lower price, the fitness tracker comparison covers Fitbit, Garmin, Amazfit and Xiaomi bands.
Every Maker Says Its Ring Is Not a Medical Device
Oura's terms of use say the services are not a medical device, are not intended to diagnose, treat, cure, mitigate or prevent any disease or medical condition, and are for wellness and informational purposes only. The same terms carve out separately regulated features where they are available, naming the Fertile Window as an example.
Samsung UK's Galaxy Ring page says Samsung Health tracking features are intended for general wellness and fitness purposes only, and not for the detection, diagnosis, treatment, monitoring or management of any medical condition. Ultrahuman's App Store listing says the Ultrahuman App and Ultrahuman Ring are not medical devices. RingConn's Gen 3 page says the product is not a medical device and that RingConn and its apps are not intended to diagnose, treat, cure or prevent any disease or medical condition.
This matters most for features such as RingConn's sleep apnea risk indicators or the Galaxy Ring's heart rate alerts. Samsung's footnote points users to a physician for medical advice, which is the right response to any worrying number.
Size the Ring With the Maker's Own Kit First
Smart ring sizes are not jewellery sizes. Oura's sizing article says its sizes differ slightly from standard US ring sizes and between generations: the Oura Ring 5 kit covers sizes 6 to 13 and the Ring 4 kit sizes 4 to 15, in whole sizes only. Oura says a properly fitting ring gives the best data accuracy and comfort, recommends the index finger, and suggests wearing the sizer for a full day, including sleep, because fingers change size through the day and night.
Ultrahuman's sizing guide explains why: the sensors must stay in constant contact with the skin, and a loose ring lets light leak in and leaves gaps in the data. It suggests keeping each sizer on for at least two nights. RingConn's Gen 3 guide says Gen 3 sizes differ from its older rings, standard rings and other brands.
Samsung UK says Galaxy Ring sizes may differ from regular ring sizes and recommends 24 hours of wear. Its page contradicts itself on the kit, citing 11 sample rings in one place and 9 sizes in another.
Battery Life, Charging and Water Ratings Vary by Brand
Oura lists 6 to 9 days for the Oura Ring 5, depending on ring size and usage, and a charge in about 80 minutes on the size-specific charger in the box. The Oura Ring 4 page lists 5 to 8 days. Samsung UK says the Galaxy Ring lasts up to 7 days, a figure its footnote says comes from testing sizes 12 and 13, and the box includes a charging case that can itself charge wirelessly.
Ultrahuman lists 4 to 6 days and a 180-minute full charge for the Ring AIR, and up to 15 days for its newer Ring PRO. RingConn's Gen 3 spec sheet lists 10 to 12 days with vibration on and 11 to 14 days with it off, a full charge in about 90 minutes and a charging case in the box.
Water is less of a split. Oura and RingConn both list IP68 and 100 metres, and Ultrahuman lists 100 metres for up to 12 hours. Samsung lists 100 metres but says the Galaxy Ring is not suitable for high-pressure water activities or diving.
The Galaxy Ring Needs an Android Phone
Phone support is the one hard stop. Samsung UK says the Galaxy Ring must pair with a phone running Android 11.0 or above with at least 1.5GB of memory, using the Galaxy Wearable and Samsung Health apps and a Samsung account, and that the Galaxy Wearable app is not supported on iOS. That rules out iPhones. Samsung's footnotes also say some features work only on selected Galaxy phones, and that the Samsung Health Monitor app is only available on Samsung Galaxy smartphones. The Samsung phone guide covers the Galaxy range.
The other three work with both platforms. Oura's setup article asks for iOS 16 or later, or Android 11 or later with Google Play services, plus Bluetooth 5.0. RingConn lists iOS 17.0 or later and Android 10.0 or later for both the Gen 3 and Gen 2 Air. Ultrahuman's Ring AIR page says iOS 15 or later and Android 6 or later, but its App Store listing asks for iOS 16.0 or later, so plan on the higher figure. The iPhone guide covers Apple's side.
Oura Membership Versus Rings With No Subscription
Oura's support article says Oura Membership provides access to all of Oura's features and data and personal guidance, including detailed sleep analysis, 24/7 heart rate, temperature monitoring, blood oxygen and women's health features. Without an active membership, it says, the app shows only the three daily scores for Readiness, Activity and Sleep, plus battery and basic settings. New members get one complimentary month.
Samsung's Amazon UK listing describes the Galaxy Ring as having no subscription fee. Ultrahuman says there are no recurring subscription fees for accessing your data, though its buy page also offers an optional paid membership for premium add-on features it calls PowerPlugs. RingConn's Gen 3 page says no subscription is required.
The table follows the sizing-first route. Oura does not sell kits on its own store, but its sizing article says a kit bought from a retailer earns a credit towards an Oura Ring from that retailer. Samsung's free kit comes with an order on its own store, and the Galaxy Ring below is a size 7 listing, so be sure of your size first.
| Product | Best for | Key specs | Price | |
|---|---|---|---|---|
 | Oura Ring 5 Sizing Kit Oura Ring 5 | Sizing Oura's slimmest ring, on iPhone or Android | Sizes 6 to 13; Ring 5: 6 to 9 days, 100 m waterproof | Check price → |
 | Oura Ring 4 Sizing Kit Wider sizes | Oura Ring 4 buyers, including sizes 4, 5, 14 and 15 | Sizes 4 to 15; Ring 4: 5 to 8 days, 100 m water resistant | Check price → |
 | Samsung Galaxy Ring, Titanium Black, Size 7 (UK version) Android | Android phone owners, Galaxy phones especially | Up to 7 days, charging case, 100 m, Android 11 or later | Check price → |
 | Ultrahuman Ring AIR Sizing Kit No subscription | Ring AIR buyers who want no recurring fees | Sizes 5 to 14; Ring AIR: 4 to 6 days, 100 m | Check price → |
 | RingConn Gen 3 Sizing Kit Long battery | Up to 14 days per charge with no subscription | Sizes 6 to 15; Gen 3: 11 to 14 days with vibration off | Check price → |