Japan uses its own ring sizing system with numbers that run from 1 upward, different from both US numbers and EU circumference values. Japanese ring sizes appear on products from Japanese brands, on import sites, and sometimes on sizing forms at international jewelry retailers that carry Japanese designs.
This guide gives you a complete Japan to US, UK, and EU conversion chart with inner diameter in mm, and explains how the Japanese system works.
Japan to US, UK, EU Ring Size Conversion Chart
| Japan size | US size | UK size | EU size | Inner diameter (mm) |
|---|---|---|---|---|
| 5 | 3.5 | G | 45.5 | 14.5 |
| 7 | 4 | H | 46.8 | 14.9 |
| 8 | 4.5 | I½ | 48 | 15.3 |
| 9 | 5 | J½ | 49.3 | 15.7 |
| 11 | 5.5 | K½ | 50.6 | 16.1 |
| 12 | 6 | L½ | 51.9 | 16.5 |
| 13 | 6.5 | M½ | 53.1 | 16.9 |
| 14 | 7 | N½ | 54.4 | 17.3 |
| 15 | 7.5 | O½ | 55.7 | 17.7 |
| 16 | 8 | P½ | 57.2 | 18.2 |
| 18 | 8.5 | Q½ | 58.5 | 18.6 |
| 20 | 9 | R½ | 59.7 | 19.0 |
| 22 | 10 | T½ | 62.2 | 19.8 |
| 24 | 11 | V½ | 64.8 | 20.6 |
| 27 | 12 | X½ | 67.2 | 21.4 |
| 30 | 13 | Z | 69.7 | 22.2 |
How the Japanese Ring Size System Works
Japan's ring sizing system is loosely based on the inner circumference in millimeters, but uses a different numbered scale than the EU system. The numbers are lower than EU sizes and do not exactly match any other system. Japan size 14, for example, is equivalent to US size 7 and EU 54.
The scale increases with each size but not in exactly uniform millimeter steps throughout the range, which is why a simple formula does not work for all conversions. The chart above maps each Japan size to its exact equivalent in the other systems.
What Japan Sizes Are Most Common
The average ring size in Japan for women is typically around Japan size 9 to 11 (US 5 to 5.5), which is slightly smaller than the US average. For men, Japan size 14 to 16 (US 7 to 8) is common. Japanese jewelry brands and retailers usually stock sizes 9 to 17 as standard.
If you are buying from a Japanese brand and need to find your size, measure your inner circumference in mm, then compare it against the EU column of the chart above, since EU values are closest to a direct circumference reading. For the paper strip method, see how to measure ring size with string or paper.
Converting Between Japan and Other Systems
The most reliable path is always through the mm diameter column. Measure your finger in mm and find your Japan size directly from the chart. For a broader view of all international sizing systems in one place, see our guide to converting ring sizes between countries.
If you are buying a ring from a Japanese brand for someone in the US or UK, share the inner diameter in mm with the US or UK jeweler rather than quoting a Japan size number. Most Western jewelers will not recognize Japanese size numbers but will always understand mm.
FAQ
What is Japan ring size 14 in US?
Japan size 14 is US size 7, UK N½, EU 54.4, with an inner diameter of 17.3mm.
Is Japanese ring sizing the same as European?
No. Japanese sizes use a different numbered scale. Japan 14 is roughly EU 54, but the numbers are not the same. Always use the conversion chart or inner diameter in mm.
What is the average ring size in Japan?
The average women's ring size in Japan is approximately Japan size 9 to 11 (US 5 to 5.5). Men typically range from Japan 14 to 16 (US 7 to 8).
How do I convert a Japanese ring size to US?
Use the chart on this page. Find your Japan size in the left column and read across to the US column. Japan 14 is US 7, Japan 12 is US 6, Japan 16 is US 8.
