About Measure Ring Size
Measure Ring Size is a free online tool that helps you find your ring size at home, without printing anything or downloading an app. It works on any phone, tablet or computer, in eleven languages, and it will always be free to use.
How the measurement works
Every screen has a different pixel density, so the first step is calibration: you place a standard bank card (or a ruler) against the screen and adjust an on-screen outline until it matches. Bank cards follow the ISO/IEC 7810 ID-1 standard — 85.6 mm wide everywhere in the world — which lets us calculate exactly how many millimeters each pixel of your screen represents.
After calibration, you place a ring on the screen and match an adjustable circle to its inner edge, or enter your finger circumference measured with a strip of paper. The result is converted instantly to US, UK, EU/ISO, Italian and Russian sizes using the ISO 8653 standard.
How accurate is it?
With careful calibration, measurements are accurate to roughly 0.5 mm, which is about half a ring size — sufficient for most purchases. For rings that are difficult or impossible to resize, we recommend confirming your size with a professional ring gauge at a jeweler.
Contact
Found a mistake or have a suggestion? Use the "Found a mistake?" link in the footer of any page — reports go straight to the developer. The tool is actively maintained and your feedback directly shapes what gets improved.
Related pages
Ring Size Chart
Complete ring size chart with US, UK, EU/ISO, Italian and Russian sizes plus inner diameter in mm. Find your size or convert between all systems.
How to Measure Ring Size
Learn how to measure your ring size at home: with our free online sizer, an existing ring, string or paper, or a ruler. Includes tips and a conversion table.