Ring Size Converter

Convert a size

How it works

Every system describes the same circle. The EU size is simply the inside circumference in millimeters (the ISO convention), the US scale steps the inside diameter up by about 0.81 mm per full size, and UK sizes are letters advancing a half-letter per US half size. This tool looks everything up in the standard published size table rather than interpolating, so the figures match the charts jewelers print — circumference is π × diameter, reported rounded the way the table states it.

Measuring: the most reliable home method is measuring the inside diameter of a ring that already fits, straight across the center of the band, in millimeters. A string or paper strip around the finger gives the circumference, but it stretches and slips, and fingers change size with temperature and time of day — measure in the evening, and never so tight the strip indents the skin.

A jeweler's sizing is the authority. Tables like this one get you to the right size for ordering; a jeweler's ring mandrel and sizers settle it exactly, and band width matters too — wide bands wear tighter than narrow ones at the same stated size. For an expensive or non-returnable ring, confirm in person.

Frequently asked questions

What is a US size 7 in EU and UK? US 7 = EU 54 (17.3 mm inside diameter, 54.4 mm circumference) = UK N.

What if my measurement falls between sizes? This tool returns the nearest table size. Most jewelers suggest sizing up when you are between sizes, especially for wide bands or if your knuckle is larger than the base of your finger.

Are men's and women's sizes different scales? No — the US, UK, and EU scales are the same for everyone; only the commonly stocked ranges differ.