US to Japan ring size converter
Japanese ring sizes follow the JIS standard, a numeric scale based on inner diameter in roughly 1/3 mm steps. The numbers do not line up with EU numbers even though both are numeric. A US 6 is about a Japan 11, and a US 7 is about a Japan 14. Convert your size below.
Quick answer
A US 7 is 14 in Japan (about 54.4 mm inner circumference). Use the converter for your exact size, or the chart below for the full range.
Between two sizes? Size up for a comfortable fit, see how to measure accurately.
US → Japan at a glance
- 4 = 7
- 5 = 9
- 6 = 11
- 7 = 14
- 8 = 16
- 9 = 19
- 10 = 21
- 11 = 24
US to Japan ring size chart
| USUS / Canada | JPJapan | mmCircumference | mmDiameter |
|---|---|---|---|
| 4 | 7 | 46.7 | 14.9 |
| 4½ | 8 | 48.0 | 15.3 |
| 5 | 9 | 49.3 | 15.7 |
| 5½ | 10 | 50.5 | 16.1 |
| 6 | 11 | 51.8 | 16.5 |
| 6½ | 13 | 53.1 | 16.9 |
| 7 | 14 | 54.4 | 17.3 |
| 7½ | 15 | 55.6 | 17.7 |
| 8 | 16 | 56.9 | 18.1 |
| 8½ | 18 | 58.2 | 18.5 |
| 9 | 19 | 59.5 | 18.9 |
| 9½ | 20 | 60.7 | 19.3 |
| 10 | 21 | 62.0 | 19.7 |
| 10½ | 22 | 63.3 | 20.1 |
| 11 | 24 | 64.6 | 20.5 |
| 11½ | 25 | 65.8 | 21.0 |
| 12 | 26 | 67.1 | 21.4 |
Japanese sizes measure across, not around
This is the difference that catches people out. American, British and European sizes all describe the distance around the inside of the band. Japanese sizes describe the distance straight across it, the inner diameter.
Japanese size 1 is a 13 mm inner diameter, and each step adds about a third of a millimetre. Because a diameter is roughly three times smaller than the circumference it belongs to, Japanese numbers behave quite differently from European ones even though both look like plain numbers.
Why Japanese numbers climb so quickly
A single US size is 2.55 mm of circumference, which is only about 0.81 mm of diameter. Since Japanese sizes advance every third of a millimetre of diameter, one US size covers roughly two and a half Japanese sizes.
That is why a US 6 is about a Japan 11 while a US 7 is about a Japan 14. The gap is not an error in the chart, it is the two scales counting different things at different resolutions. It also means Japanese sizing is finer than American sizing, so a Japanese jeweller can offer a closer fit.
Ordering from Japan, China or Korea
The same JIS numbers are widely used in China and South Korea, so a size that works for a Tokyo retailer will usually be understood elsewhere in the region. Sizes commonly run from about 1 to 27.
If a listing gives a diameter in millimetres alongside the size number, use the diameter. It removes any doubt about which scale the seller means, and the converter above takes a diameter directly.
Common questions
How do I convert a US ring size to Japan?
Enter your US size in the converter above and read the Japan result, or find your row in the chart below. Every value is calculated from the ring’s inner circumference, so it works in both directions.
What is a US 7 in Japan?
A US 7 is 14 in Japan. That ring has an inner circumference of about 54.4 mm.
Related conversions
Or see the full ring size chart.