Smart ring size comparison
Every major smart ring side by side: sizing system, range, kit, price and US availability. Treat your jewelry size as a starting point, then confirm with the brand’s sizing process.
| Ring | System | Sizes | Kit | Price | US? |
|---|---|---|---|---|---|
| Oura Ring 4 | Proprietary whole numbers (US-style, no half sizes) | Sizes 4–15 | Use the Oura Ring 4 sizing kit; Size Later includes a complimentary kit, and many retailers sell kits with purchase credit. | Check Oura | available |
| Oura Ring 5 | Proprietary whole numbers (redesigned interior) | Sizes 6–13 | Use the Oura Ring 5 sizing kit; do not rely on Ring 4 kit results as a final order size. | Check Oura | available |
| Samsung Galaxy Ring | US size labels (5–15) | Sizes 5–15 | Use the Galaxy Ring sizing kit before ordering; Samsung recommends wearing a sample for more than 24 hours. | $399.99 | available |
| RingConn Gen 2 | Proprietary, with a published mm chart | Sizes 6–14 | Free sizing kit, a 3D-print template, or borrow-and-measure. | ~$299 | available |
| Ultrahuman Ring AIR | Proprietary (plastic sizers) | Sizes 5–14 | Free plastic sizing kit on order. | ~$349 | check status |
| Circular Ring 2 | US-style whole sizes, with app-camera "Digital Ring Sizing" | Sizes 6–14 | App-camera sizing by default; an optional physical kit is about $5. | ~$379 and up | available |
| Evie Ring | Proprietary (women-focused, open gap design) | Sizes ~5–12 | Free sizing kit recommended before ordering. | ~$269 | available |
Does my normal ring size carry across brands?
Oura Ring 4: Oura uses whole-number sizes that are close to US labels, but the final fit is brand-specific. Do not order from a jewelry size alone — use the Oura Ring 4 sizing kit and wear the sample for at least 24 hours, including sleep.
Oura Ring 5: Oura says Ring 5 sizing is slightly different from Ring 4. If you know an old Ring 4 size, treat it only as a starting point and confirm with the Ring 5 sizing kit before ordering.
Samsung Galaxy Ring: The Galaxy Ring is labeled in US sizes, but Samsung warns your usual size may not be the best fit because of the sensors inside. Use the kit and wear the sample for more than 24 hours before choosing.
RingConn Gen 2: RingConn publishes inner-diameter and circumference measurements for its sizes, so you can compare them with a standard chart. Still, RingConn recommends its sizing kit because biometric rings need a secure, comfortable fit.
Ultrahuman Ring AIR: Ultrahuman Ring AIR uses its own sizing kit, and Ultrahuman says Ring AIR sizes may differ slightly from standard US ring sizes. Use the kit rather than ordering from a jewelry-size conversion alone.
Circular Ring 2: Circular says Ring 2 follows standard US-style whole sizes, but its help center also recommends using its digital sizing flow and notes sizing can run about a half size above standard. Follow the app carefully and re-check if the fit feels loose.
Evie Ring: The Evie Ring is designed for women and uses a slightly open band that flexes, but it still relies on its own sizing kit rather than your jewelry size. Order the kit and wear a sample before buying.
Frequently asked questions
Is the Oura Ring the same size as the Samsung Galaxy Ring?
Not exactly. Oura uses its own whole-number sizes, while the Galaxy Ring is labeled in US sizes. Both brands recommend checking fit through their sizing process before ordering.
Which smart ring has the widest size range?
Among the models tracked here, Oura Ring 4 and Samsung Galaxy Ring have the broadest published ranges. Always check the current brand kit before ordering.
Do any smart rings use normal ring sizes?
Some brands use US-style labels or publish millimetres, but the final fit is still brand-specific because smart rings need sensor contact.