Japan to US ring size
Convert a Japan ring size to US in one step. Enter your Japan size and read the US equivalent, or use the full chart below.
Japan to US ring size chart
| Japan size | US size | Diameter (mm) |
|---|---|---|
| 4 | 3 | 14.1 |
| 5 | 3.5 | 14.5 |
| 7 | 4 | 14.9 |
| 8 | 4.5 | 15.3 |
| 9 | 5 | 15.7 |
| 10 | 5.5 | 16.1 |
| 12 | 6 | 16.5 |
| 13 | 6.5 | 16.9 |
| 14 | 7 | 17.3 |
| 15 | 7.5 | 17.7 |
| 16 | 8 | 18.1 |
| 17 | 8.5 | 18.5 |
| 18 | 9 | 19 |
| 19 | 9.5 | 19.4 |
| 20 | 10 | 19.8 |
| 22 | 10.5 | 20.2 |
| 23 | 11 | 20.6 |
| 24 | 11.5 | 21 |
| 25 | 12 | 21.4 |
| 26 | 12.5 | 21.8 |
| 27 | 13 | 22.2 |
Japan and US ring sizes describe the same physical bands with different labels. Because every size maps to a real inside diameter in millimetres, the conversion between Japan and US is exact, not an approximation. If you know the diameter of a ring that already fits, you can confirm both the Japan and the US size from the millimetre column.
The most looked-up conversions on this page: a Japan 12 is a US 6, a Japan 14 is a US 7, and a Japan 18 is a US 9. Women's rings most often fall around Japan 12 to 14, while men's rings cluster near Japan 18 and above.
If your size sits between two rows, size up. It is easier to pad or resize a ring that is a touch loose than to stretch one that will not clear your knuckle. For a hands-on check, print the true-scale ring sizer and match a ring you own.
Common questions
What is a Japan 14 ring size in US?
A Japan 14 ring is a US 7. Both labels describe the same band with an inside diameter of 17.3 mm.
How do I convert a Japan ring size to US?
Find your Japan size in the chart and read across to the US column, or use the converter above. Both point to the same physical band diameter, so the conversion is exact.
Is a Japan ring size the same as US?
No, the labels differ, but the bands are the same physical sizes. The chart lines up each Japan size with its US equivalent and the diameter in millimetres.
What if my size falls between two values?
Choose the larger size. A slightly loose ring can be resized or padded, but a ring that is too small will not pass the knuckle.
Last reviewed and updated on July 2, 2026. Conversion tables are checked against published international sizing standards.