Ring size conversion chart
Ring sizes are just the inside diameter or circumference of the band. Measure your finger's circumference with a strip of paper, divide by π (3.14) to get the diameter, then read across the chart. Measure at the end of the day when fingers are largest.
| Inside diameter (mm) | US | UK | EU (circumference mm) | JP |
|---|---|---|---|---|
| 14.0 | US 3 | F | 44 | 4 |
| 14.9 | US 4 | H½ | 47 | 7 |
| 15.7 | US 5 | J½ | 49 | 9 |
| 16.5 | US 6 | L½ | 52 | 11 |
| 17.3 | US 7 | N½ | 54 | 14 |
| 18.1 | US 8 | P½ | 57 | 16 |
| 19.0 | US 9 | R½ | 59 | 18 |
| 19.8 | US 10 | T½ | 62 | 20 |
| 20.6 | US 11 | V½ | 64 | 23 |
| 21.4 | US 12 | X½ | 67 | 25 |
| 22.2 | US 13 | Z½ | 69 | 27 |
| 23.0 | US 14 | Z+1 | 72 | 30 |
Notes
- EU sizes are the inner circumference in mm (diameter × π).
- Between sizes? Choose the larger for wide bands, the smaller for thin bands.
- Knuckles bigger than the base? Measure the knuckle and size to it.
Measure the finger, not a ring you own
The most reliable result comes from measuring the finger itself, because an old ring may be worn, resized or never have fitted properly. Wrap a thin strip of paper or a piece of non-stretchy string snugly around the base of the finger, mark where the ends meet, and measure that length in millimetres — that is your circumference. Dividing the circumference by π (3.14) gives the inside diameter, the figure most charts are built around. Measure at the end of the day, when fingers are at their largest, and avoid doing it after exercise, in the cold or after a lot of salt, all of which change finger volume enough to shift a size.
Diameter versus circumference: why the scales disagree
Ring sizing systems do not all measure the same thing, which is why a single finger can be "size 7" in one country and "54" in another. US and UK sizes are essentially diameter-based scales, with US using whole and half numbers and UK using letters. European sizes are the inside circumference in millimetres, so a US 7 with a 17.3 mm diameter is EU 54 (close to 17.3 × 3.14). Japanese sizes are their own numbered scale, where the same finger is a 14. When you convert, always start from the diameter or circumference and read across, rather than trying to map numbers between scales directly.
The knuckle problem and wide bands
A ring has to pass over the knuckle and then sit securely on the base, and those two diameters are not always equal. If your knuckle is noticeably wider than the base of your finger, size to the knuckle, otherwise the ring will not go on — a slightly loose band can be adjusted later, but one that will not clear the joint cannot. Band width matters too: wide bands feel tighter for the same size because they contact more of the finger, so jewellers usually recommend going up half a size for anything 6 mm or wider and staying true to size for a thin 2 mm band. Temperature and time of day also nudge the fit.
Confirm before you commit
Paper and string methods are good estimates, but they stretch and compress, so they can land you half a size off. If the ring matters — an engagement or wedding band — confirm with a physical ring sizer or a jeweller's gauge before ordering, and ideally measure twice on different days. For online orders, check the return and resizing policy first, because resizing a band with stones or a tension setting is not always possible. Between two sizes, the safer default is the larger one for a wide band and the smaller one for a thin band, since a ring that spins is easier to live with than one that will not pass the knuckle.
Frequently asked questions
- How do I measure my ring size at home?
- Wrap a thin strip of paper snugly around the finger, mark the overlap, measure the length in mm — that is the circumference; divide by 3.14 for the diameter and read the chart.
- What is US size 7 in EU?
- US 7 has an inside diameter of 17.3 mm, which is EU size 54 (circumference), UK N½ and JP 14.
- Do ring sizes differ for men and women?
- The scales are identical; average sizes differ — women commonly US 5–7, men US 9–11.