Ring Size Conversion
Convert ring sizes across US, UK, ISO (EU), Japan and Korea, with diameter and circumference in mm.
International Ring Size Chart
| US | UK | ISO / EU | JP / KR | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|---|
| 3 | F | 44 | 4 | 14.1 | 44.2 |
| 3.5 | G | 46 | 5 | 14.5 | 45.5 |
| 4 | H | 47 | 7 | 14.9 | 46.8 |
| 4.5 | I | 48 | 8 | 15.3 | 48 |
| 5 | J | 49 | 9 | 15.7 | 49.3 |
| 5.5 | K | 51 | 10 | 16.1 | 50.6 |
| 6 | L | 52 | 12 | 16.5 | 51.9 |
| 6.5 | M | 53 | 13 | 16.9 | 53.1 |
| 7 | N | 54 | 14 | 17.3 | 54.4 |
| 7.5 | O | 56 | 15 | 17.7 | 55.7 |
| 8 | P | 57 | 16 | 18.1 | 57 |
| 8.5 | Q | 58 | 18 | 18.6 | 58.3 |
| 9 | R | 60 | 19 | 18.9 | 59.5 |
| 9.5 | S | 61 | 20 | 19.4 | 60.8 |
| 10 | T | 62 | 21 | 19.8 | 62.1 |
| 10.5 | U | 63 | 23 | 20.2 | 63.4 |
| 11 | V | 65 | 24 | 20.6 | 64.6 |
| 11.5 | W | 66 | 25 | 21 | 65.9 |
| 12 | X | 67 | 26 | 21.4 | 67.2 |
| 12.5 | Y | 68 | 27 | 21.8 | 68.5 |
| 13 | Z | 70 | 28 | 22.2 | 69.7 |
| 13.5 | Z1 | 71 | 28+ | 22.6 | 71 |
| 14 | Z2 | 72 | 28+ | 23 | 72.3 |
ISO, EU, France and Germany all label rings by the inner circumference in millimetres, so the ISO / EU number is the same across Continental Europe. Japan (号) and Korea (호) share one scale. JP sizes above 28 are approximate.
Conversion Charts
Popular Sizes
How to Measure Ring Size
- Measure at the end of the day when fingers are largest
- Ensure the ring fits over your knuckle
- Measure in normal temperature (fingers swell in heat)
- Consider ring width: wider bands need larger sizes
No sizer to hand? Print our ring sizer with diameter circles and a wrap strip, or read the full ring measuring guide.
ISO sizes represent inner circumference in millimeters, the international standard for ring sizing. Japan and Korea size by diameter instead, so their numbers are much smaller. See ring sizes around the world for every national system.