Convert Japanese numeric ring sizes to Australian and UK letter sizes with a practical calculator, complete Japanese-to-Australian ring size chart, millimetre measurements and expert fit guidance for international jewellery orders.
Japanese jewellery commonly uses numeric sizes such as 7, 9, 11, 12 or 13. Commercial charts often call this the Japan Custom Size or JCS system. The number itself is not the circumference in millimetres, so a Japanese size 12 does not mean 12 mm. Instead, JP 12 has an inner circumference close to 52.36 mm.
The Japanese Standards Association lists JIS S 4700:2022 for jewellery ring-size definition, measurement and designation. Japanese retail charts may still present familiar customary whole numbers for consumers.
Australian jewellers generally use the British alphabetical scale. Sizes appear as letters such as K, L, M, N and P, with half sizes written as Kยฝ, Lยฝ or Mยฝ. Many sellers describe this as the AU/UK scale because the same letter notation is used in both markets.
Because a Japanese whole-size step and an Australian half-letter step are not exactly equal, a conversion may be rounded. Always retain the circumference or inner diameter as the physical reference.
Results are nearest practical matches. A retailer may round differently where a Japanese size falls between Australian full or half letters.
| Japanese Size | Australian / UK | Circumference (mm) | Inner Diameter (mm) | EU Approx. | US Approx. | Range |
|---|---|---|---|---|---|---|
| 1 | Cยฝ | 40.84 | 13.00 | 41 | 3 | Very small |
| 2 | D | 41.89 | 13.33 | 42 | 3 | Very small |
| 3 | E | 42.94 | 13.67 | 43 | 3 | Very small |
| 4 | F | 43.98 | 14.00 | 44 | 3 | Small |
| 5 | Fยฝ | 45.03 | 14.33 | 45 | 3.5 | Small |
| 6 | Gยฝ | 46.08 | 14.67 | 46 | 3.5 | Small |
| 7 | Hยฝ | 47.12 | 15.00 | 47 | 4 | Small |
| 8 | I | 48.12 | 15.32 | 48 | 4.5 | Small |
| 9 | Jยฝ | 49.22 | 15.67 | 49 | 5 | Common |
| 10 | K | 50.27 | 16.00 | 50 | 5.5 | Common |
| 11 | L | 51.31 | 16.33 | 51 | 6 | Common |
| 12 | M | 52.36 | 16.67 | 52 | 6 | Common |
| 13 | Mยฝ | 53.41 | 17.00 | 53 | 6.5 | Common |
| 14 | Nยฝ | 54.45 | 17.33 | 54 | 7 | Common |
| 15 | Oยฝ | 55.50 | 17.67 | 56 | 7.5 | Common |
| 16 | P | 56.55 | 18.00 | 57 | 8 | Common |
| 17 | Q | 57.60 | 18.33 | 58 | 8 | Mediumโlarge |
| 18 | R | 58.65 | 18.67 | 59 | 8.5 | Mediumโlarge |
| 19 | Rยฝ | 59.69 | 19.00 | 60 | 9 | Mediumโlarge |
| 20 | Sยฝ | 60.74 | 19.33 | 61 | 9.5 | Mediumโlarge |
| 21 | Tยฝ | 61.78 | 19.67 | 62 | 10 | Mediumโlarge |
| 22 | U | 62.83 | 20.00 | 63 | 10.5 | Mediumโlarge |
| 23 | V | 63.88 | 20.33 | 64 | 10.5 | Extended |
| 24 | Vยฝ | 64.92 | 20.66 | 65 | 11 | Extended |
| 25 | Wยฝ | 65.97 | 21.00 | 66 | 11.5 | Extended |
| 26 | Xยฝ | 67.02 | 21.33 | 67 | 12 | Extended |
| 27 | Y | 68.07 | 21.67 | 68 | 12.5 | Extended |
| 28 | Zยฝ | 69.11 | 22.00 | 69 | 13 | Extended |
| 29 | Z+1 | 70.16 | 22.33 | 70 | 13 | Extended |
| 30 | Z+2 | 71.21 | 22.67 | 71 | 13.5 | Extended |
Print at 100% actual size. Check the 50 mm calibration line with a physical ruler before placing a ring over the circles. Match the ring's inside edge, not the outside metal.
Japanese labels are discrete numbers and should be matched through circumference.
Australia uses UK-style letters, often including half sizes.
A 16.67 mm diameter gives approximately 52.37 mm circumference.
A 54.45 mm circumference gives approximately 17.33 mm diameter.
5.236 cm equals 52.36 mm.
There is no reliable simple addition or subtraction rule between the labels.
Measure the finger that will wear the ring. Left and right hands can differ, and a measurement from another finger is not a safe substitute.
Wrap a strip approximately 5 mm wide around the finger base. Keep it snug without compressing the skin and check that the loop can pass over the knuckle.
Lay the strip flat and measure from its starting edge to the overlap mark. Enter the result as circumference in the calculator.
Measure at least three times, ideally at different times of day. Avoid immediately after exercise, cold exposure or a hot shower.
Wide bands usually feel tighter. Ask the Australian retailer whether the design needs an additional half-size allowance.
Use a ring that already fits the intended finger and is not visibly bent or oval.
Measure straight across the widest inner point through the centre. Do not include the metal walls.
Turn the ring 90 degrees and repeat. Different readings suggest an out-of-round ring that should be checked professionally.
The calculator converts the diameter into circumference and finds the nearest Japanese size and Australian letter.
| Japanese | Australian Approx. | Circumference | Diameter | Typical Use |
|---|---|---|---|---|
| 7 | Hยฝ | 47.12 mm | 15.00 mm | Small finger / pinky |
| 9 | Jยฝ | 49.22 mm | 15.67 mm | Small ring finger |
| 11 | L | 51.31 mm | 16.33 mm | Common narrow-band range |
| 12 | M | 52.36 mm | 16.67 mm | Frequently searched conversion |
| 13 | Mยฝ | 53.41 mm | 17.00 mm | Common ring-finger range |
| 16 | P | 56.55 mm | 18.00 mm | Medium to larger fit |
| 20 | Sยฝ | 60.74 mm | 19.33 mm | Common men's range |
| 25 | Wยฝ | 65.97 mm | 21.00 mm | Large / extended range |
Japanese national standard listing for jewellery ring-size definition, measurement and designation.
Japanese-size examples with inside diameter and finger circumference values.
Japanese JCS, UK/Australia, Europe and diameter conversion references.
Australian alphabetical scale, circumference, diameter and international conversion guidance.
International framework for ring-size measurement and designation.