There are a variety of ring sizing systems used around the world. The most common systems include the US, British, French, German, and Japanese variations.
It’s crucial to make sure that you order according to the sizing system the jeweler your dealing with uses. For instance, all Sorella rings are sized according to the US ring sizing system. So you’d want to know what your US ring size is.
Ideally you should have your finger sized by a professional jeweler and he or she can provide you with the conversion to the sizing system you need. But, we’ve found a handy dandy online tool that does a darn good job of converting ring size among the different systems. If you have an existing ring that fits but you don’t know the size, the tool can also translate diameter or circumference (measured in millimeters or inches)to the different sizing systems also.
You can find the tool here: Online Ring Size Conversion ToolPosted by Sorella