Quick answer
A US ring size 7 is UK N½, EU 54.5, Japan 14 and Swiss 14.5: an inside diameter of 17.3 mm.
The European (ISO) ring size is simply the inside circumference of the ring in millimeters, which makes it the easiest to measure. The US uses numbers, the UK and Australia use letters, and Japan and China use their own numbering.
Find your size in any column and read across the row; the last column gives the finger circumference that each size fits.
Ring size conversion chart
| US | UK | EU · ISO | Japan · China | Swiss | Diameter | Circumference |
|---|---|---|---|---|---|---|
| 3 | F½ | 44 | 4 | 4 | 14.1 | 44–45 mm |
| 3½ | G½ | 45.5 | 5 | 5.5 | 14.5 | 45–46 mm |
| 4 | H½ | 47 | 7 | 7 | 14.9 | 46–47 mm |
| 4½ | I½ | 48 | 8 | 8 | 15.3 | 47–49 mm |
| 5 | J½ | 49.5 | 9 | 9.5 | 15.7 | 49–50 mm |
| 5½ | K½ | 50.5 | 10 | 10.5 | 16.1 | 50–51 mm |
| 6 | L½ | 52 | 12 | 12 | 16.5 | 51–53 mm |
| 6½ | M½ | 53 | 13 | 13 | 16.9 | 53–54 mm |
| 7 | N½ | 54.5 | 14 | 14.5 | 17.3 | 54–55 mm |
| 7½ | O½ | 55.5 | 15 | 15.5 | 17.7 | 55–56 mm |
| 8 | P½ | 57 | 16 | 17 | 18.1 | 56–58 mm |
| 8½ | Q½ | 58.5 | 17 | 18.5 | 18.5 | 58–59 mm |
| 9 | R½ | 59.5 | 18 | 19.5 | 18.9 | 59–60 mm |
| 9½ | S½ | 61 | 19 | 21 | 19.4 | 60–61 mm |
| 10 | T½ | 62 | 20 | 22 | 19.8 | 61–63 mm |
| 10½ | U½ | 63.5 | 22 | 23.5 | 20.2 | 63–64 mm |
| 11 | V½ | 64.5 | 23 | 24.5 | 20.6 | 64–65 mm |
| 11½ | W½ | 66 | 24 | 26 | 21.0 | 65–67 mm |
| 12 | Y | 67 | 25 | 27 | 21.4 | 67–68 mm |
| 12½ | Z | 68.5 | 26 | 28.5 | 21.8 | 68–69 mm |
| 13 | Z+1 | 69.5 | 27 | 29.5 | 22.2 | 69–70 mm |
Calculated from the standard definitions (US: 0.032 in per size; UK: 1.25 mm per letter). Wide bands fit tighter: go up half a size.
How to measure your ring size
- Wrap a thin strip of paper around the base of the finger.
- Mark where the paper overlaps, then lay it flat and measure the length in millimeters.
- Find that circumference in the last column. Measure at the end of the day, when fingers are slightly larger.
- For a wide band (over 6 mm), go up half a size.
Questions
What is the most common ring size?
For women, US 6 to 7 (EU 52–54.5); for men, US 9 to 10 (EU 59–62).
Is the EU ring size the circumference?
Yes. The ISO (European) size is the inside circumference in millimeters: size 54 fits a finger of about 54 mm.