Size chart

You can easily measure ring size in mm (millimetres).
Use your ruler to measure the diameter of the ring by placing the ruler against the ring. Make sure that the beginning of the ruler is placed on the left side. Then read the measurement in mm. Now use the chart below to convert the size from mm to the regular US ring size.

 

US Ring Size	Ring Size Diameter in mm
4	14.9 mm
4.5	15.3 mm
5	15.7 mm
5.5	16.1 mm
6	16.5 mm
6.5	16.9 mm
7	17.3 mm
7.5	17.7 mm
8	18.1 mm
8.5	18.5 mm
9	19.0 mm
9.5	19.4 mm
10	19.8 mm
10.5	20.2 mm
11	20.6 mm
11.5	21.0 mm