Ring Size Converter
Convert ring size between US, EU, UK, Japan and inside diameter in mm. US 7 is EU 54 and 17.3 mm across, UK N½ and Japan 14. With a printable sizer strip. How it works
Use the Ring Size Converter
About the Ring Size Converter
US ring size 7 is EU size 54, with an inside diameter of 17.3 mm and an inside circumference of 54.4 mm. In the UK and Australia it is N½ and in Japan 14. The ring size converter works in US, EU, UK and Japanese sizes and inside diameter in millimeters or inches; each EU size is the inside circumference rounded to a whole millimeter.
US ring sizes 3 to 13 with EU size, diameter and circumference
| US size | EU size | Inside diameter (mm) | Inside circumference (mm) |
|---|---|---|---|
| 3 | 44 | 14.1 | 44.2 |
| 4 | 47 | 14.9 | 46.8 |
| 5 | 49 | 15.7 | 49.3 |
| 6 | 52 | 16.5 | 51.9 |
| 7 | 54 | 17.3 | 54.4 |
| 8 | 57 | 18.1 | 57.0 |
| 9 | 60 | 18.9 | 59.5 |
| 10 | 62 | 19.8 | 62.1 |
| 11 | 65 | 20.6 | 64.6 |
| 12 | 67 | 21.4 | 67.2 |
| 13 | 70 | 22.2 | 69.7 |
The converter’s own chart, which lists whole sizes from US 0 to US 27. EU is the circumference rounded to whole millimeters. Half sizes follow the same straight line.
UK and Japanese ring sizes for US 3 to 13
| US size | UK / Australia | Japan | EU size |
|---|---|---|---|
| 3 | F | 4 | 44 |
| 4 | H | 7 | 47 |
| 5 | J½ | 9 | 49 |
| 6 | L½ | 11 | 52 |
| 7 | N½ | 14 | 54 |
| 8 | P½ | 16 | 57 |
| 9 | R½ | 18 | 60 |
| 10 | T½ | 20 | 62 |
| 11 | V½ | 23 | 65 |
| 12 | X½ | 25 | 67 |
| 13 | Z½ | 27 | 70 |
UK letters and Japanese sizes from the equivalency table in Wikipedia’s Ring size article, as the converter shows them. Japanese sizes do not follow the diameter in a straight line, so they cannot be worked out from it.
How to use this tool
- Type a size in the US, EU or Diameter field. The other two fields and the circumference fill in.
- Open the full reference chart to see US 0 to 27 with EU, diameter and circumference.
- To measure at home, show the printable strip, print it at 100% scale and check with a ruler that it is 110 mm long from its start edge to the far end before you wrap it around the finger. Read the size where the start edge meets the scale.
Frequently asked questions
- What is a size 7 ring in mm?
- US 7 is 17.3 mm inside diameter and 54.4 mm inside circumference, which is EU size 54. In inches the diameter is 0.682 in; the converter takes a diameter in either unit.
- How do I convert ring size to mm?
- Inside diameter in mm = (0.458 + 0.032 × US size) × 25.4. US 9 gives 18.9 mm and US 5 gives 15.7 mm. Multiply the diameter by π for the circumference.
- How do I convert an EU ring size to a US size?
- Type the EU size in the EU field. EU 52 is 52 mm around and 16.6 mm across, which the converter shows as US 6. EU 54 is US 7. A US size worked out from EU or diameter is shown to the nearest half size.
- How do I measure my ring size at home?
- Wrap a strip of paper around the finger, mark where it overlaps and measure that length in millimeters: it is your inside circumference, which is the EU size. Type it in the EU field, so a 57 mm strip reads as US 8. Or measure straight across the inside of a ring that fits and type that in the Diameter field: 18.1 mm is also US 8.
- Does it convert UK or Japanese ring sizes?
- Yes. Type a UK or Australian letter such as N½ (N 1/2 also works) or a Japanese size such as 14, and the US, EU and diameter fill in: both are US 7, EU 54, 17.3 mm across. The letters run from A to Z4 and the Japanese sizes from 1 to 27, as the Wikipedia equivalency table lists them; a US size with no Japanese size within a quarter size, such as US 14, shows none.
- What does EU ring size mean?
- It is the inside circumference in millimeters, as defined in ISO 8653. EU 50 is 50 mm around, about 15.9 mm across. Some countries use circumference minus 40 mm or the plain diameter, so check which system a shop means.
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