US & Canada Sizes: This system uses numbers (and sometimes fractions) to denote ring sizes. Sizes typically range from around 3 to 13.5 for adults, with half and quarter sizes available. This is perhaps the most commonly referenced system when talking about “standard sizes” in North America.
UK & Australia Sizes: This system uses letters (with half sizes) to indicate ring sizes, starting from G (or smaller for children) going up to Z+ sizes for larger sizes. It’s another form of standard sizing but is geographically specific.
European Sizes: This system is numerical like the US system but uses a different scale based on the inner circumference of the ring in millimeters. It typically ranges from about 38 to 70.
