A complete Japanese ring size guide for 2026 โ measure your finger or an existing ring, calculate the nearest Japan size, compare US, UK and EU conversions, understand useful Japanese terminology, and shop confidently in Tokyo, Osaka, Kyoto, Nagoya, Fukuoka or online.
Print at 100% or actual size. Confirm the 50 mm calibration line before placing a comfortable ring over a circle. Match the inside edge, not the outside metal wall.
About 52.4 mm circumference corresponds to Japanese size 12.
Each whole Japanese size adds about one-third of a millimetre to diameter.
A 17 mm inner diameter gives approximately 53.4 mm circumference.
A 55.5 mm circumference gives about 17.67 mm inner diameter.
Japanese size 12 is approximately US size 6.
Japanese size 14 is close to EU 54โ55.
The calculator selects the nearest whole Japanese size. Some bridal and custom jewellers can make half sizes.
| ๐ฏ๐ต Japan | ๐ Diameter (mm) | โญ Circumference (mm) | ๐ช๐บ EU Approx. | ๐บ๐ธ US Approx. | ๐ฌ๐ง UK Approx. | Range |
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Left and right hands can differ, so measure the finger that will actually wear the ring.
Cold weather can make fingers smaller, while heat, exercise and bathing may make them fuller.
Stiff printer paper may leave gaps; use a narrow flexible strip that follows the finger closely.
A circumference near 49.2 mm points to Japanese size 9; around 52.4 mm points to size 12.
Use the same tension and compare readings on another day.
Wide rings usually feel tighter than narrow rings of the same nominal size.
Use a Japanese jeweller's metal sizing rings or sizing kit for bridal, custom and difficult-to-resize designs.
The reference ring must fit the exact intended finger.
Do not include the metal walls. The empty opening is the inner diameter.
A calliper makes the one-third-millimetre Japanese steps easier to identify.
15.67 mm is approximately Japan 9; 16.67 mm is Japan 12; 18.00 mm is Japan 16.
A wide comfort-fit ring may feel different from a narrow flat-edged ring.
Japanese rings are commonly labelled 1ๅท, 8ๅท, 12ๅท or 15ๅท. Size 1 has an inner diameter near 13.0 mm, and each whole size increases diameter by roughly one-third of a millimetre. This produces an increase of a little over one millimetre in circumference per size.
Examples: Japan 9 is about 15.67 mm diameter and 49.2 mm circumference; Japan 12 is about 16.67 mm diameter and 52.4 mm circumference; Japan 15 is about 17.67 mm diameter and 55.5 mm circumference.
Some jewellers refer to JIS-based sizing, JCS/Japan Custom Size or simply ๆฅๆฌใตใคใบ. State the physical dimensions as well as the number when ordering internationally.
Ring size.
Ring size using a loanword.
Gล / size number.
Inner diameter.
Inside circumference.
Finger circumference.
Engagement ring.
Wedding ring.