Ring Size Converter
Diameter or circumference → US, UK, EU and ISO ring sizes.
See how it works
Watch a quick simulation of this tool in action — no file needed.
How to use Ring Size Converter
Follow these steps — everything happens instantly in your browser.
- 1
Step 1. Switch to “From diameter” or “From circumference” depending on what you measured.
- 2
Step 2. Enter the value in millimeters.
- 3
Step 3. Read your ring size in US, UK (letter), EU, and ISO formats.
Why use this tool
Private by design
All processing happens locally in your browser. Open DevTools → Network and you'll see zero file uploads. Ever.
Instant
No upload wait, no queue, no server round-trip. Results appear the moment you drop a file.
Free & unlimited
No accounts, no watermarks, no daily caps. Use it as many times as you like, forever.
Works everywhere
Desktop, tablet or phone — every tool is responsive and installable as a PWA for offline use.
Frequently asked questions
Everything you might want to know about ring size converter.
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