Ring Size Converter
Convert US ring sizes to millimeter diameter and EU sizes.
US size
7
Inside diameter
17.3 mm
Circumference / EU size
54.4 mm
One millimeter of stakes
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.
Measuring at home
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.
Frequently asked questions
- How does the Ring Size Converter work?
- Convert US ring sizes to millimeter diameter and EU sizes.
- Is the Ring Size Converter free to use?
- Yes. The Ring Size Converter is completely free, runs entirely in your browser, and requires no account or sign-up. Your inputs never leave your device.
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