Ring Size Converter

Ring sizes measure the inside of a ring. A US size 7 is a UK N and an EU 54, with an inner circumference of 54.4 mm and a diameter of 17.3 mm. This converter covers US sizes 3 to 13 in half sizes, UK letters F to Z and EU sizes 44 to 69.

The EU system is the easiest to understand. The size is the inner circumference in millimeters, rounded, so an EU 54 ring measures about 54 mm around the inside. US sizes go up in half steps of roughly 1.3 mm of circumference. The UK and Australia use letters, with each letter about one US half size. So you can convert by measuring alone.

To find your size at home, wrap a thin strip of paper around the base of your finger, mark where it overlaps and measure the length in millimeters. Then choose Circumference (mm) and enter it. You can also measure the inside diameter of a ring that fits and choose Diameter (mm). The tool picks the closest size in its chart and shows all three systems with the exact circumference and diameter. Fingers change size through the day. They swell when warm and shrink when cold. Measure at the end of the day at a normal room temperature. If you fall between two sizes, go for the larger one. Wide bands, about 6 mm or more, fit tighter, so many jewelers suggest going up half a size. For other sizes, try the Shoe Size Converter.