Ring Size Converter
Convert ring sizes between US, UK, EU (circumference), and JP standards, or measure from diameter.
100% client-side · no upload
How to use
- Measure the inside diameter of an existing ring with a ruler or calipers.
- Enter the diameter in millimetres and click Convert.
- The closest standard size in US, UK, EU, and JP systems is shown instantly.
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Frequently Asked Questions
- Is the ring size converter free?
- Yes, completely free with no signup and no usage limits.
- Does my data leave my device?
- No. All conversions run in JavaScript inside your browser. Nothing is sent to any server.
- Does it work on mobile?
- Yes. The tool is mobile-first and works on iPhone Safari and Android Chrome.
- How do I measure my ring diameter?
- Place an existing ring on a ruler and measure the inside diameter (the gap across the interior of the ring) in millimetres. Alternatively, wrap a thin strip of paper around your finger, mark where it overlaps, then measure the length — this is the circumference. Divide by π (3.14159) to get the diameter.
- What is EU ring size?
- EU ring sizes are measured in millimetres of circumference (the length around the inside of the ring). A US size 7 ring has a circumference of approximately 55.7 mm, which corresponds to EU size 55.7.
Last updated: By jarvisbox