Oura Ring Size Chart
A third-party Oura size reference labeled 6-13, with UK/Australia equivalents and internal diameter.
Third-party Oura size reference (6-13)
Oura provides separate model-specific sizing guides and a sizing kit; use this table only as a rough estimate.
| US Size | UK / Australia | Internal Diameter (mm) | Circumference (mm) | Approx. (cm) |
|---|---|---|---|---|
| US Size6 | UK / AustraliaL 1/2 | Internal Diameter (mm)16.45 | Circumference (mm)51.6 | Approx. (cm)5.16 cm |
| US Size7 | UK / AustraliaN 1/2 | Internal Diameter (mm)17.3 | Circumference (mm)54.4 | Approx. (cm)5.44 cm |
| US Size8 | UK / AustraliaP 1/2 | Internal Diameter (mm)18.2 | Circumference (mm)57.2 | Approx. (cm)5.72 cm |
| US Size9 | UK / AustraliaR 1/2 | Internal Diameter (mm)19 | Circumference (mm)59.7 | Approx. (cm)5.97 cm |
| US Size10 | UK / AustraliaT 1/2 | Internal Diameter (mm)19.8 | Circumference (mm)62.3 | Approx. (cm)6.23 cm |
| US Size11 | UK / AustraliaV 1/2 | Internal Diameter (mm)20.6 | Circumference (mm)64.9 | Approx. (cm)6.49 cm |
| US Size12 | UK / AustraliaX 1/2 | Internal Diameter (mm)21.4 | Circumference (mm)67.5 | Approx. (cm)6.75 cm |
| US Size13 | UK / AustraliaZ+1 | Internal Diameter (mm)22.2 | Circumference (mm)70.1 | Approx. (cm)7.01 cm |
Oura Ring sizing works differently from a regular ring
Oura Rings are worn snugly for their health sensors to maintain skin contact, so their fit can differ from a ring you'd wear loosely for jewelry. Oura publishes separate guides for Oura Ring 4 and Gen3 and provides a sizing kit before shipping your actual ring — use the guide and kit for your specific model rather than relying on this table or your regular ring size alone.
For a standard-ring measurement conversion, try the ring size calculator.
Frequently asked questions
Is my regular ring size my Oura Ring size?
Usually not directly. Oura publishes separate sizing guides for the Gen3 and Ring 4, and its sizes run differently from standard jewelry sizing — which is why Oura ships a sizing kit before your actual ring. Use this table for orientation, then size with the kit for your exact model.
What’s the difference between Gen3 and Ring 4 sizing?
Each generation has its own official sizing guide and kit, and the fit characteristics differ slightly between models. Never assume a Gen3 size transfers to a Ring 4 (or vice versa) without re-testing with the correct kit.
Which finger should an Oura Ring go on?
Oura recommends the index or middle finger for the most reliable sensor readings, since the sensors need steady skin contact. The ring finger works if the fit is snug; avoid the thumb and pinky, where readings degrade.
What if I’m between Oura sizes?
Size up and confirm with the kit: a slightly looser smart ring still tracks, while a too-tight one gets uncomfortable overnight when fingers swell. Wear the kit sizer for at least 24 hours, including sleep, before locking in a size.