Ring Size Converter

US sizes step ~0.81 mm of diameter per whole size; EU sizes just use the circumference in millimeters. A quarter size — 0.2 mm — separates comfortable from spinning, which is why jewelers size with graduated mandrels rather than charts.

Wrap a paper strip snugly where the ring sits, mark the overlap, and measure in millimeters — that's the EU size directly. Measure at day's end at room temperature (fingers shrink in cold), and size wider bands a quarter up.