Cm to mm Ring Size Converter

Convert your ring measurements (cm, mm, inches) to find your perfect ring size in US, UK, EU, and other international standards.

Measurements

Millimeters (mm)
Centimeters (cm)
Inches (in)
Millimeters (mm)
Centimeters (cm)
Inches (in)
Equivalent Ring Sizes
US / Canada --
UK / Australia --
EU / ISO --
Japan --

How to measure your ring size

Finding the right ring size is crucial for comfort. If you don't have a professional ringizer tool, you can measure it at home using a simple method.

Method 1: Measure an existing ring

If you have a ring that fits the intended finger well:

  1. Take the ring and a ruler.
  2. Measure the inside diameter of the ring (do not include the metal thickness).
  3. Enter the value in the "Inside Diameter" field above to find your size.

Method 2: Measure your finger

  1. Cut a thin strip of paper or use a piece of string.
  2. Wrap it around the base of the finger you want to measure. make sure it's snug but can still slide over your knuckle.
  3. Mark the point where the paper/string overlaps.
  4. Measure the length from the end to the mark with a ruler. This is your Inside Circumference.
  5. Enter this value in the "Inside Circumference" field above.

Tips for Accuracy

  • Measure your finger at the end of the day when it is likely to be largest.
  • Avoid measuring when your hands are cold, as fingers can shrink.
  • If you fall between two sizes, it's usually safer to go with the larger size.