Updated
Jewelry
Ring Size Converter
Convert ring sizes across US, UK, EU/ISO and Japan (approx), calculate size from diameter or circumference, and get a quick wide-band adjustment estimate.
US, UK, EU/ISO Ring Size Converter with Diameter & Circumference
Enter a ring size or measurement and instantly see the equivalent sizes and measurements in multiple systems.
Conversion charts can vary slightly due to rounding and different standards. Use this to narrow your size, then confirm with a jeweler or the seller’s official sizing method for best fit.
For the best accuracy, measure 2–3 times and use the average. If your knuckle is larger than the base of your finger, choose a size that can pass the knuckle comfortably without spinning too loosely.
Wide bands often feel tighter than thin bands, especially when passing over the knuckle. This estimator gives a practical adjustment to test before ordering.
Use this chart when you have a measurement and want the nearest standardized size. If you are between sizes, consider band width and comfort preference before deciding.