Japan
Ring sizes in Japan.
Japanese sizes follow JIS S 4700: size 1 is 13 mm of inside diameter, and each size adds one third of a millimetre. It is one of the cleanest scales in the world — strictly linear, and defined to a ±0.02 mm tolerance.
- The number means
- JIS 号数: size 1 = 13 mm diameter, ⅓ mm per size
- Written as
- a whole number — 号 (gō)
Japan sizes converted
Every row is calculated from the published standards, so the columns stay consistent with one another.
Scroll the table sideways to see every region
| Japan | Diameter | Circum. | US / CA | UK / AU | EU / ISO | France | DE / NL |
|---|---|---|---|---|---|---|---|
| 7 | 14.88 mm | 46.8 mm | 4 | H½ | 47 | 47 | 15 |
| 8 | 15.29 mm | 48.0 mm | 4½ | I½ | 48 | 48 | 15.5 |
| 9 | 15.69 mm | 49.3 mm | 5 | J½ | 49.5 | 49.5 | 15.5 |
| 10 | 16.10 mm | 50.6 mm | 5½ | K½ | 50.5 | 50.5 | 16 |
| 12 | 16.51 mm | 51.9 mm | 6 | L½ | 52 | 52 | 16.5 |
| 13 | 16.91 mm | 53.1 mm | 6½ | M½ | 53 | 53 | 17 |
| 14 | 17.32 mm | 54.4 mm | 7 | N½ | 54.5 | 54.5 | 17.5 |
| 15 | 17.73 mm | 55.7 mm | 7½ | O½ | 55.5 | 55.5 | 17.5 |
| 16 | 18.13 mm | 57.0 mm | 8 | P½ | 57 | 57 | 18 |
| 18 | 18.54 mm | 58.2 mm | 8½ | Q½ | 58 | 58 | 18.5 |
| 19 | 18.95 mm | 59.5 mm | 9 | R½ | 59.5 | 59.5 | 19 |
| 20 | 19.35 mm | 60.8 mm | 9½ | S½ | 61 | 61 | 19.5 |
| 21 | 19.76 mm | 62.1 mm | 10 | T½ | 62 | 62 | 20 |
| 22 | 20.16 mm | 63.3 mm | 10½ | U½ | 63.5 | 63.5 | 20 |
| 24 | 20.57 mm | 64.6 mm | 11 | V½ | 64.5 | 64.5 | 20.5 |
| 25 | 20.98 mm | 65.9 mm | 11½ | W½ | 66 | 66 | 21 |
| 26 | 21.38 mm | 67.2 mm | 12 | X½ | 67 | 67 | 21.5 |
| 27 | 21.79 mm | 68.5 mm | 12½ | Z | 68.5 | 68.5 | 22 |
| 29 | 22.20 mm | 69.7 mm | 13 | Z+1 | 69.5 | 69.5 | 22 |
Need a standard that isn’t shown? The full conversion chart lists all11 side by side.
Calibration
Calibrate with something in your pocket.
You don’t need a bank card. Our sizer knows the published diameter of coins from your currency, so you can calibrate with whatever is nearest.
¥500
26.5 mm across
Japan Mint coin specifications
¥100
22.6 mm across
Japan Mint coin specifications
€1
23.25 mm across
European Central Bank coin specifications
Buying from abroad
If you’re ordering from a retailer that uses a different scale, don’t translate the size yourself and hope. Send them the inside diameter in millimetres — every workshop in the world can work from that, and it removes the rounding step where errors creep in.
The reason is that the scales have different step sizes. A whole size in one system rarely lands exactly on a whole size elsewhere, so somebody has to round. Better that it’s the jeweller holding your measurement than a chart guessing at it.