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? |
|---|---|---|---|---|---|
| RingConn Gen 3 | Generation-specific whole-number sizes; not standard US sizes | Sizes 6–15 | Choose the Gen 3 sizing kit. Test the sample for 24 hours, including sleep and daily activities, before submitting your size. | Check RingConn | available |
| 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) | Historical sizes ~5–12 | New orders and shipments are currently paused, so an active sizing-kit flow is not confirmed. | Availability unverified | available |
Does my normal ring size carry across brands?
RingConn Gen 3: RingConn says Gen 3 fit differs from standard jewelry sizes and other RingConn generations. A US number is only a starting sample choice. Confirm with the Gen 3 kit; do not copy a Gen 2 number into your order.
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 lists US-style whole-size labels, while its official sizing page also notes that Ring 2 can run about a half size above standard. Treat neither statement as an automatic conversion: follow Circular’s digital sizing flow or physical-kit guidance and confirm the final fit before ordering.
Evie Ring: Current availability could not be verified. The last recorded official notice paused new orders and shipments. The live source was unavailable at the latest check; historical sizes, prices and kit details are not current purchase guidance.
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.