Use the chart below for conversion of US and Canadian number sizes to the "Wheat sheaf" system of letter sizes used in the U.K., Australia, Ireland, etc. Diameters and circumferences are also given in both inches and millimeters. Note that the measurements for the US are accurate while the other measurement systems are approximate. The reason is that the conversions don’t always give standard, even results; so a standard Swiss size could result in uncommon fractions if converted to the US sizes.
Ring sizing gauges and finger gauges as well as published charts do not always agree with one another. There are also several ways of reading ring size gauges, which can lead to some discrepancies if you go from one jewelry store to another. The ring sizing information presented here is the result of a comparison of various sources and methods and has proven to be accurate. For more sizes, please click the link below.