Ring Size Guide 1.Find a piece of string or strip of paper no wider than 1.4 cm (1/2 inc). 2. Wrap the paper or string around the finger to be sized. 3.Use a pen to mark the point on the string/paper where it overlaps, forming a complete circle. 4. Measure the mark from the end of the length of paper or string with a ruler.Use the metric side for more accurate sizing. Ring Size GuideRing SizeDiameterCircumference414.9 mm46.8 mm4.515.3 mm48.0 mm515.7 mm49.3 mm5.516.1 mm50.6 mm616.5 mm51.9 mm6.516.9 mm53.1 mm717.3 mm54.4 mm7.517.7 mm55.7 mm818.2 mm57.0 mm8.518.5 mm58.3 mm919.0 mm59.5 mm9.519.4 mm60.8 mm1019.8 mm62.1 mm10.520.2 mm63.4 mm1120.6 mm64.6 mm11.521.0 mm65.9 mm1221.4 mm67.2 mm12.521.8 mm68.5 mm