We specifiy the ring sizes by the inner circumference of the ring in millimetre (mm).
You can easily determine your own ring size with a measuring tape or a cord. To measure simply place the cord (or the measuring tape) around the finger where you want to put the ring. The ends of the cord should be marked.
Use a ruler to measure the cord and determine your ring size in mm. Easy!
Then use the PDF chart to find your ring size!