Put the ring that fits you the most on top of a ruler and measure its inside diameter from side to side of the inside circle.
- 15 mm diameter (one centimeter and five mm) – the size of your ring is US 5
- 16 mm diameter (one centimeter and six mm) – the size of your ring is US 6
- 17 mm diameter (one centimeter and seven mm) – the size of your ring is US 7
- 18 mm diameter (one centimeter and 8 mm) – the size of your ring is US 8
- 19 mm diameter (one centimeter and 9 mm) – the size of your ring is US 9
