There are different ways of measuring ring sizes. the most common way however is measuring by diameter, measured in milimeters. On average this is the same as the thickness of your finger.
Ring sizes we have in stock are most often between 17 and 20, where 17 means a ring size of a diameter of 17mm, a quite small ring size, mostly suitable for girls between 10 and 15 years of age. A ring size of 18mm can be worn by women between 16 and 20 years old, while a ring size of 19mm is mostly used by women above 20 years. Do pay attention though! These ages are guidelines. If you have small hands for your age, it is better to take a ring with a smaller size. A ring size of 20 is very large for a woman. Rings we have in stock with this size are often worn by men of 20 years and older.
Many of our rings are so called 'open' rings. This means that they have a subtle opening at the back and therefore are quite flexible when we are talking about ring sizes. Actually, they are sort of 'pinched' around your finger.
Hope this information helped in finding the correct ring size.