Ring Size Guide

Finding the perfect ring size is crucial for comfort and fit. To ensure accuracy, it’s helpful to compare both the Japanese and USA ring sizes alongside the inner diameter (measured in millimeters). At Precious Lab we use Japan Size. For the best results, measure your finger’s inner diameter or use a ring sizer to determine the most accurate size before making your purchase. Here’s a comprehensive guide for easy conversion:
US Size Precious Lab (Japan Size) Inner Diameter (mm)
3 1/4 5 14.3
3 1/2 14.5
3 3/4 6 14.7
4 14.9
4 1/8 7 15
4 1/4 15.1
4 1/2 8 15.3
4 3/4 15.5
5 9 15.7
5 1/4 15.9
5 3/8 10 16
5 1/2 16.1
5 3/4 11 16.3
6 16.5
6 1/4 12 16.7
6 1/2 16.9
6 5/8 13 17
6 3/4 17.1
7 14 17.3
7 1/4 17.5
7 1/2 15 17.7
7 3/4 17.9
7 7/8 16 18
8 18.1
8 1/4 17 18.3
8 1/2 18.5
8 3/4 18 18.7
9 18.9
9 1/8 19 19
9 1/4 19.2
9 3/8 20 19.3
9 1/2 19.4
9 3/4 19.6
9 7/8 21 19.7
10 19.8
10 1/4 22 20
10 1/2 20.2
10 5/8 23 20.3
10 3/4 20.4
11 20.6
11 1/8 24 20.7
11 1/4 20.8
11 1/2 25 21