Ring Size Converter
Convert a ring size between UK letters, US and Canadian numbers, European, German, Italian and Japanese sizes, or find your size from a finger measurement in millimetres.
About this tool
This uses the ISO 8653 comparison table, which defines ring sizes by inner circumference in millimetres. UK, Irish and Australian sizes are letters in steps of 1.25 mm with half sizes; US and Canadian sizes go up in quarters; France and most of Europe use the circumference itself; Germany uses the inner diameter; and Italy, Spain and Switzerland use the circumference minus 40.
The easiest home measurement is a strip of paper around your finger, measured flat, or the inside diameter of a ring that already fits multiplied by 3.14. Measure at the end of the day when fingers are largest, and go up a quarter to half a size for wide bands.