We highly recommend getting sized by a local jeweler and asking for your US ring size. If that's not available, you can try the following method:
Ring SIZING guide
WRAP
Start by wrapping a string, a strip of paper, or a measuring tape around the finger you want to measure.
MARK
Carefully mark the point where the ends meet.
MEASURE
Use a ruler and measure the length that you marked on your measuring tool.
SELECT YOUR SIZE
| (mm) | US |
| 46.5 mm | 4 |
| 49.3 mm | 5 |
| 51.9 mm | 6 |
| 54.4 mm | 7 |
| 57.0 mm | 8 |
| 59.5 mm | 9 |
| 62.1 mm | 10 |
| 64.6 mm | 11 |
| 67.2 mm | 12 |