Wrapit around the base of the appropriate finger. Make sure the paper fits snugly. You should be able to slip it over your knuckle. Using a pen – mark the point on the paper where it overlaps forming a complete circle. Measure the length from the starting end of the paper to the pen mark using a ruler with a millimeter measurement. Placethe ring on top of each circle until you find the perfect match. You can tell you have the right measurement when your ring fits neatly inside the circle. Double check your measurements for accuracy. Ring Size (US) Diameter (Millimeters) Diameter (Centimeters) 3. Measurethe marked route. The result in millimetres corresponds to your ring size. Example: A length of 5.4 cm corresponds to ring size 54. Perform control measurements to compensate for measurement fluctuations. Repeat steps 1 - 3 a few times and then work out the mean value of your measurements. ZHxJ.