Find your ring size across US, UK, EU, Japan, and China sizing — by finger diameter, finger circumference, or a size you already know.
C = π × D, then the closest row in a US / UK / EU / Japan / China chart is chosen. Starting from a known size just looks up that row. Manufacturer tolerances differ, so treat this as the nearest standard size.
Measure the inside diameter of a ring that already fits (in millimeters).
Wrap a strip of paper or string around your finger, mark where it overlaps, and measure that length (in millimeters).
Already know your size in one system? See the equivalent in every other system.
| US | UK | EU | Japan | China | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|---|---|
| 3 | F | 44 | 4 | - | 14.1 | 44.2 |
| 3.5 | G | 45 | 5 | - | 14.5 | 45.5 |
| 4 | H | 46.5 | 7 | 8 | 14.8 | 46.8 |
| 4.5 | I | 47.5 | 8 | 9 | 15.2 | 47.8 |
| 5 | J | 49 | 9 | 10 | 15.7 | 49.3 |
| 5.5 | K | 50 | 10 | 11 | 16.1 | 50.6 |
| 6 | L | 51.5 | 12 | 12 | 16.5 | 51.9 |
| 6.5 | M | 52.5 | 13 | 13 | 16.9 | 53.1 |
| 7 | N | 54 | 14 | 14 | 17.3 | 54.4 |
| 7.5 | O | 55 | 15 | 15 | 17.7 | 55.7 |
| 8 | P | 56.5 | 16 | 16 | 18.1 | 57.0 |
| 8.5 | Q | 58 | 17 | 17 | 18.5 | 58.3 |
| 9 | R | 59 | 18 | 18 | 18.9 | 59.5 |
| 9.5 | S | 60 | 19 | 19 | 19.4 | 60.9 |
| 10 | T | 61.5 | 20 | 20 | 19.8 | 62.1 |
| 10.5 | U | 63 | 21 | 21 | 20.2 | 63.5 |
| 11 | V | 64 | 22 | 22 | 20.6 | 64.6 |
| 11.5 | W | 65.5 | 23 | 23 | 21.0 | 65.9 |
| 12 | X | 67 | 24 | 24 | 21.4 | 67.2 |
| 12.5 | Y | 68 | 25 | 25 | 21.8 | 68.5 |
| 13 | Z | 69.5 | 26 | 26 | 22.2 | 69.7 |
Either works, since they're mathematically related (circumference = π × diameter), but circumference is usually easier to measure accurately at home — wrap a strip of paper or string around the finger and measure its length.
Each region developed its own sizing standard independently — US and Canada use a numeric scale, the UK uses letters, and the EU and Japan use different numeric scales based on circumference. The chart maps them to each other by matching the underlying measurement, not by any shared numbering logic.
Round up rather than down for comfort. A ring that's slightly loose is safer day-to-day than one that's tight, and most jewelers can resize a ring down by a half-size afterward if needed.
No — temperature and time of day can shift finger size noticeably, and it can also change gradually over the years. Measure at a normal body temperature, not right after exercise or in cold weather, for the most consistent result.