There is several different ring size systems used worldwide. However, We are using the Hong Kong measurement system to define the size of ring. Thus, in the following we provide a table convert different ring size into Hong Kong size.
Ring Size Chart
| Inter- Diameter (mm)  | 
Hong Kong Size  | 
American Size  | 
United Kingdom Size  | 
Japan Size  | 
Switzerland Size  | 
|---|---|---|---|---|---|
| 14.1 | 6 | 3 | F | 4 | 4 | 
| 14.3 | 7 | 3.25 | F 1/2 | 5 | 5.25 | 
| 14.7 | 8 | 3.75 | G | 6 | 6.5 | 
| 14.9 | 9 | 4 | H | 7 | 7 | 
| 15.3 | 10 | 4.5 | I | 8 | 8.5 | 
| 15.7 | 11 | 5 | J 1/2 | 9 | 9.5 | 
| 16.1 | 12 | 5.5 | K 1/2 | 10 | 10.5 | 
| 16.5 | 13 | 6 | L 1/2 | 11 | 12.75 | 
| 16.7 | 14 | 6.25 | M | 12 | 13.5 | 
| 17.1 | 15 | 6.75 | N | 13.5 | 14.5 | 
| 17.3 | 16 | 7 | N 1/2 | 14 | 15.25 | 
| 17.7 | 17 | 7.5 | O 1/2 | 15 | 16.5 | 
| 18.2 | 18 | 8 | P 1/2 | 16.25 | 18.25 | 
| 18.5 | 19 | 8.5 | Q 1/2 | 17 | 18.75 | 
| 18.8 | 20 | 9.75 | R | 17.5 | 19 | 
| 19.1 | 21 | 9.25 | S | 18 | 20 | 
| 19.4 | 22 | 9.5 | S 1/2 | 19 | 20.75 | 
| 19.8 | 23 | 10 | T 1/2 | 20 | 21.75 | 
| 20.2 | 24 | 10.5 | U 1/2 | 22 | 22.75 | 
| 20.6 | 25 | 11 | V 1/2 | 23 | 24.75 | 
| 21.0 | 26 | 11.5 | W 1/2 | 24 | 26.25 | 
| 21.2 | 27 | 12 | X | 24.5 | 26.75 | 
| 21.6 | 28 | 12.25 | Y | 25.5 | 28 | 
| 22.0 | 29 | 12.5 | Z 1/2 | 26.5 | 29 |