Ring Sizes
Accessories · 6 specs
Direct Answer
Ring sizes are globally standardized under ISO 8653 by measuring the exact internal circumference of the band in millimeters. Sized numerically in the US (1 to 13), alphabetically in the UK (A to Z), by circumference in Europe (41 to 70 mm), and numerically in Japan (1 to 27), standard charts map inner diameters with precision.
Source: ISO 8653:2016 / BS 1283 / ANSI Jewellery Standards · Last reviewed Aug 28, 2026
Specs
| Governing Standards | ISO 8653 / BS 1283 / ANSI Jewellery Specifications |
| ISO 8653 Definition | Direct inside circumference in millimeters (e.g., Size 52 = 52.0 mm circumference) |
| US / Canada Sizing | Numerical scale 1 to 13 (0.032" / 0.81 mm increase in diameter per full size) |
| UK / Australia Sizing | Alphabetical scale A to Z (half sizes designated as L 1/2, M 1/2) |
| Japan / Asia Sizing | Numerical scale 1 to 27 based on inner diameter |
| Wide Band Rule | Order 1/2 size larger for ring bands wider than 6.0 mm (0.24") |
International Ring Size Conversion Table
| Inside Diameter (mm) | Inside Circ. (ISO mm) | US & Canada | UK & Australia | Europe (EU / ISO) | Japan (JP) |
|---|---|---|---|---|---|
| 14.86 mm | 46.7 mm | US 4.0 | UK H | 47 | JP 7 |
| 15.27 mm | 48.0 mm | US 4.5 | UK I 1/2 | 48 | JP 8 |
| 15.70 mm | 49.3 mm | US 5.0 | UK J 1/2 | 49 | JP 9 |
| 16.10 mm | 50.6 mm | US 5.5 | UK L | 51 | JP 10 |
| 16.51 mm | 51.9 mm | US 6.0 | UK M | 52 | JP 11 |
| 16.92 mm | 53.1 mm | US 6.5 | UK N | 53 | JP 12 |
| 17.32 mm | 54.4 mm | US 7.0 | UK O | 54 | JP 14 |
| 17.75 mm | 55.8 mm | US 7.5 | UK P | 56 | JP 15 |
| 18.14 mm | 57.0 mm | US 8.0 | UK Q | 57 | JP 16 |
| 18.53 mm | 58.3 mm | US 8.5 | UK R | 58 | JP 17 |
| 18.95 mm | 59.5 mm | US 9.0 | UK S | 60 | JP 18 |
| 19.35 mm | 60.8 mm | US 9.5 | UK T | 61 | JP 19 |
| 19.76 mm | 62.1 mm | US 10.0 | UK U | 62 | JP 20 |
| 20.17 mm | 63.4 mm | US 10.5 | UK V | 63 | JP 22 |
| 20.57 mm | 64.6 mm | US 11.0 | UK W | 65 | JP 23 |
| 21.39 mm | 67.2 mm | US 12.0 | UK Y | 67 | JP 25 |
| 22.20 mm | 69.7 mm | US 13.0 | UK Z+1 | 70 | JP 27 |
Knuckle Transit and Temperature Sizing Rules
- Time of Day & Temperature: Fingers shrink in cold conditions and swell by up to half a size in high heat or in the evening. Measure fingers at room temperature at the end of the day.
- Knuckle Sizing: If your knuckle is significantly wider than the base of your finger, measure both the knuckle and the base and choose a size halfway between them.