I already have a ring
1. Take a ring you already have with the right size, and place it on a ruler.
2. Measure the inner diameter.
3. Find diameter in the chart below.
If you don't have a ring
1. Take a piece of thread, wrap the thread around your finger - don’t pull.
2. Measure the length of the thread with your ruler.
3. Find circumference in the chart below.
| US Size | Diameter | Circumference |
| 3.5 | 14.5 mm | 45.5 mm |
| 4 | 14.9 mm | 46.7 mm |
| 4.5 | 15.2 mm | 47.97 mm |
| 5 | 15.7 mm | 49.3 mm |
| 6 | 16.5 mm | 51.9 mm |
| 7 | 17.4 mm | 54.5 mm |
| 8 | 18.1 mm | 57.15 mm |
| 9 | 18.9 mm | 59.34 mm |