Jewelry size is a social number. A smart ring is a lamp and a microphone for blood volume, taped to a finger that swells at 2 a.m. If it spins, the photoplethysmography (PPG) diodes are photographing skin that is not there. If it strangulates, you will take it off, which is the only accuracy problem that matters. Every serious maker ships a plastic sizing kit and tells you to sleep in it. Believe that paragraph more than the battery headline.
The second split is commercial. Oura sells a ring and rents the dashboard. Several rivals sell the dashboard with the ring. Samsung sells a sensor that reports to an app you may already have, on a phone you may not.
| Ring | Published battery | Recurring fee (maker's claim) | Phone catch |
|---|---|---|---|
| Oura Ring 5 / 4 (Gen3+ membership) | Ring 5 typically 6-9 days; Ring 4 typically 5-8 days (Oura, July 2026). Ring 4 lab: sizes 8-10, SpO2 off, 1 hour activity HR. | US $5.99/month or $69.99/year after one included month. Without it: three daily scores, battery, settings. | iOS and Android. Membership is the product. |
| RingConn Gen 2 | 10-12 days by size (6-7: up to 10; 8-11: up to 11; 12-14: up to 12). OSA feature may drain faster. Case claimed to add many more ring-days. | No subscription, per the product page. Listed $299. | iOS 17+, Android 10+. Sizes are not jewelry sizes and not other brands' sizes. |
| Ultrahuman Ring AIR | 4 to 6 days; about 180 minutes to full, per the spec table. | No recurring fee to access ring data, per Ultrahuman's FAQ. One-time purchase. Optional paid extras can still exist; read the current checkout. | iOS 15+, Android 6+. Sizing kit; half sizes not offered. |
| Samsung Galaxy Ring | Up to 6 days (sizes 5-11) or 7 days (12-13), per Samsung battery support. Real use is often shorter. | No subscription fee to view data in Samsung Health, per Samsung FAQ. | Android, and the useful version is a Galaxy phone. An iPhone buyer is shopping in the wrong aisle. |
Oura's published US annual membership is about $210 over three years on top of the ring. That is a magazine you should want. It is not a rounding error on a $300 to $500 piece of titanium. The $0 bars are maker claims, not a promise that every future feature stays free.
Oura Membership (US annual price, 27 July 2026); RingConn, Ultrahuman, and Samsung pages cited above · accessed 2026-08-12 · Membership bar is 3 times Oura's published $69.99 US annual price. Hardware street prices change and are omitted. Competitor $0 values are the makers' current no-required-subscription claims, not an audit of in-app purchases.
A ring that you can spin with a fingertip is photographing air. A ring you cannot get over a swollen morning knuckle will spend the night on the nightstand, which is a perfect night of missing data.
- 01Contact face
LEDs and photodiodes sit on the palmar side. If the ring rotates, they leave the artery. Snug, not tourniquet.
- 02Knuckle vs base
Jewelry often sizes the knuckle. A wearable sizes the base after 24 hours, including sleep. Makers tell you to wear the plastic overnight. Do that.
- 03Brand charts
RingConn states its sizes differ from standard rings and from other smart rings. Do not order an Oura size from a RingConn memory.
- 04Swelling
Heat, salt, and the luteal phase change circumference. If you only fit the sizer at noon in air conditioning, you have not fitted it.
Battery headlines are best-case protocols. Oura's Ring 4 write-up is unusually specific: new rings, common sizes, SpO2 off, one hour of activity heart rate. Turn SpO2 on and they say you may lose up to two days. RingConn says enabling sleep-apnea monitoring can increase drain. Ultrahuman's 4 to 6 days is the shortest published range in this set, which matters if you hate chargers. A charging case (RingConn Gen 2, Galaxy Ring) is a second battery you have to remember. A puck on the bathroom shelf (Oura) is a daily habit. Neither is 'set and forget' if the ring dies on a Thursday night and you wanted Friday's sleep score.
Are smart rings useful without a subscription is the Oura-without-membership remainder. How to interpret recovery data is what to do with a 62. The quantified self at home is the culture of living by the badge. This page is only fit, published endurance, and the bill.
Which constraint is actually yours?
Start with the fee and the phone, then the finger.
- 01I will not pay a wellness membership
Do not buy current Oura Gen3+ expecting the brochure app for free. Look at RingConn, Ultrahuman, or Galaxy Ring, and re-read their current pages.
- I also refuse AndroidGalaxy Ring is out. Compare RingConn and Ultrahuman on sizing kit plus battery, not on a roundup's favorite.
- 02I already live in Samsung Health on a Galaxy phone
The Galaxy Ring is the accessory that does not invent a second dashboard. Battery is shorter than RingConn's published range. That may still be the honest buy.
- My phone is an iPhoneShop elsewhere. Ecosystem lock is a fee paid in silicon.
- 03I want that specific Oura app and I will pay $70 a year
Price the ring plus three years of membership. Then size it like a sensor.
- The sizer spins or bites after a nightDo not 'make it work.' Return. A beautiful wrong size is a $400 mood ring.
Size, then charger, then the invoice
- 01
Sleep in the sizing kit. Brand sizes do not transfer.
- 02
Treat battery numbers as maker tests with footnotes, not as a race we ran.
- 03
Oura's US membership is a real three-year cost. The no-sub rings are a different product.
Questions
- 01Which ring is most accurate?
We did not measure that. Accuracy claims without a methods section are not a comparison. For daily use, a ring you actually wear beats a ring with a prettier scatterplot in a press deck.
- 02Can I wear it on my dominant hand?
Makers often prefer index, middle, or ring finger with the sensors toward the palm. Dominant hands take more knocks. Follow the sizing guide you bought, not a forum's pinky experiment.
- 03Is the charging case worth it?
If you travel and hate pucks, yes. If the case dies in a bag, you have two batteries to manage. Count the objects, not the marketing '150 days.'
