Ring Sizes A to Z – “Wheat Sheaf” System of Lettering (British Standard)
| Inside Diameter (mm) | Inside Circumference (mm) | Ring Size (lettering) |
|---|---|---|
| 12.0 | 37.8 | A |
| 12.2 | 38.4 | A½ |
| 12.4 | 39.1 | B |
| 12.6 | 39.7 | B½ |
| 12.8 | 40.4 | C |
| 13.1 | 41.0 | C½ |
| 13.3 | 41.6 | D |
| 13.5 | 42.3 | D½ |
| 13.7 | 42.9 | E |
| 13.9 | 43.5 | E½ |
| 14.1 | 44.2 | F |
| 14.3 | 44.8 | F½ |
| 14.5 | 45.5 | G |
| 14.7 | 46.1 | G½ |
| 14.9 | 46.7 | H |
| 15.1 | 47.4 | H½ |
| 15.3 | 48.0 | I |
| 15.5 | 48.7 | J |
| 15.7 | 49.3 | J½ |
| 15.9 | 49.9 | K |
| 16.1 | 50.6 | K½ |
| 16.3 | 51.2 | L |
| 16.5 | 51.8 | L½ |
| 16.7 | 52.5 | M |
| 16.9 | 53.1 | M½ |
| 17.1 | 53.8 | N |
| 17.3 | 54.4 | N½ |
| 17.5 | 55.0 | O |
| 17.7 | 55.7 | O½ |
| 17.9 | 56.3 | P |
| 18.1 | 56.9 | P½ |
| 18.3 | 57.6 | Q |
| 18.5 | 58.2 | Q½ |
| 18.7 | 58.9 | R |
| 18.9 | 59.5 | R½ |
| 19.2 | 60.1 | S |
| 19.4 | 60.8 | S½ |
| 19.6 | 61.4 | T |
| 19.8 | 62.1 | T½ |
| 20.0 | 62.7 | U |
| 20.2 | 63.3 | U½ |
| 20.4 | 64.0 | V |
| 20.6 | 64.6 | V½ |
| 20.8 | 65.2 | W |
| 21.0 | 65.9 | W½ |
| 21.2 | 66.5 | X |
| 21.4 | 67.2 | X½ |
| 21.6 | 67.8 | Y |
| 21.8 | 68.4 | Z |
