Ring Size Converter
Compare ring size systems in one chart. Choose both systems and a size to see all listed matches.
Reference chart: Tiffany & Co. UK and Japan guides, checked October 2026; US 3–13 in half sizes only. EU is the published circumference rounded to whole millimeters, and cm/inches are derived from that circumference. Measurements and international labels are approximate; confirm with the jeweler. Blank entries are unavailable in the source.
Size labels are not universal measurements. The chart uses the cited mappings and preserves multiple listed matches. A missing match is shown as —. Check the relevant brand or standard before selecting a product.
How to use this tool
- Choose the source and destination from the selectors.
- Select a source size. The result includes every listed match.
- Use Swap to reverse the selected systems, or Load example for a valid starting value.
Frequently asked questions
Can I reverse the conversion?
Yes. Swap systems, then choose a source size. A size can have several matches; the chart does not treat them as exact interchangeable measurements.
Why can a value show an error?
Only values present in the source chart are listed. Missing equivalents are not interpolated or guessed. After swapping a result with multiple matches, choose which source size you mean.
How precise is the result?
The published chart determines the matches. Brands and products can differ; see the notes and sources.
Sources
Last updated: 2026-10-30