1. Have your finger measured by a jeweler who uses a ring sizer gauge (a series of rings of different sizes that are tried on to find the size that best fits your finger) or a ring band mandrel. (An existing ring is placed over the mandrel in order to measure the inside circumference.
2. Measure or determine the inside circumference of a ring that fits well.
To measure you finger place a ring that fits well (a wedding band for example) on a ring size chart. When the inside of your ring touches the exterior of the circle exactly, you have found your size.
Please make sur that the page that appears on your screen is the real size and that before the chart is printed there have been no scale changes.
You can also obtain your ring size using a slide caliper or slide guage and a ring the fits well.
The equivalence allows you to see your ring size right away.