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International Ring Size Conversion Chart
| FACTRON rings are machined and cannot be resized. Please order the correct size. For wide-sized rings, one size larger is recommended. | |||||
| Inside diameter mm | Circum ferece mm | Japan | International standards | US & Canada | UK |
| 16.0 | 50.3 | 10 | 50 | 5.5 | K |
| 16 1/3 | 51.3 | 11 | 51 | 6 | L |
| 16 2/3 | 52.4 | 12 | 52 | 6.5 | L-M |
| 17.0 | 53.4 | 13 | 53 | 6.5-7 | M-N |
| 17 1/3 | 54.5 | 14 | 54 | 7-7.5 | N-O |
| 17 2/3 | 55.5 | 15 | 55 | 7.5-8 | O-P |
| 18.0 | 56.6 | 16 | 56 | 8 | P |
| 18 1/3 | 57.6 | 17 | 57 | 8.5 | Q |
| 18 2/3 | 58.6 | 18 | 58 | 9 | R |
| 19.0 | 59.7 | 19 | 59 | 9.5 | S |
| 19 1/3 | 60.7 | 20 | 60 | 10 | T |
| 19 2/3 | 61.8 | 21 | 61 | 10-10.5 | T-U |
| 20.0 | 62.8 | 22 | 62 | 10.5 | U |
| 20 1/3 | 63.9 | 23 | 63 | 11 | V |
| 20 2/3 | 64.9 | 24 | 64 | 11.5 | W |
| 21.0 | 66.0 | 25 | 65 | 12 | X |
| 21 1/3 | 67.0 | 26 | 66 | 12.5 | Y |
| 21 2/3 | 68.1 | 27 | 67 | 13 | Z |
| 22.0 | 69.1 | 28 | 68 | ||
| 22 1/3 | 70.2 | 29 | 69 | ||
| 22 2/3 | 71.2 | 30 | 70 | ||
| 23.0 | 72.3 | 31 | 71 | ||
| 23 1/3 | 73.3 | 32 | 72 | ||
| 23 2/3 | 74.3 | 33 | 73 | ||
| 24.0 | 75.4 | 34 | 74 | ||