Ring Size Converter
Convert ring sizes between US/Canada, UK/Australia letters, inner diameter and inner circumference (ISO 8653).
US/Canada size
7
- UK/Australia
- N½
- Inner diameter
- 17.3 mm (0.68 in)
- Inner circumference (ISO 8653)
- 54.4 mm
- Italy, Spain, Switzerland
- 14.4
Charts differ by a fraction of a size between jewelers. Wide bands fit tighter — go up a quarter to a half size.
US sizes 3–13
| US | Diameter | Circumference | UK/AU |
|---|---|---|---|
| 3 | 14.1 mm | 44.2 mm | F½ |
| 4 | 14.9 mm | 46.8 mm | H½ |
| 5 | 15.7 mm | 49.3 mm | J½ |
| 6 | 16.5 mm | 51.9 mm | L½ |
| 7 | 17.3 mm | 54.4 mm | N½ |
| 8 | 18.1 mm | 57 mm | P½ |
| 9 | 18.9 mm | 59.5 mm | R½ |
| 10 | 19.8 mm | 62.1 mm | T½ |
| 11 | 20.6 mm | 64.6 mm | V½ |
| 12 | 21.4 mm | 67.2 mm | X½ |
| 13 | 22.2 mm | 69.7 mm | Outside A–Z |
How it works
US/Canada size s: inner diameter = 11.63 + 0.8128 × s mm (0.032 in per size); ISO 8653 size = inner circumference in mm = π × diameter; UK/Australia letters step 1.25 mm of circumference, with C = 40 mm
Questions
- How does the ring size converter work?
- US/Canada size s: inner diameter = 11.63 + 0.8128 × s mm (0.032 in per size); ISO 8653 size = inner circumference in mm = π × diameter; UK/Australia letters step 1.25 mm of circumference, with C = 40 mm.
- What do I need to enter?
- I know my, Size. Optional fields can be left blank.
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