Northern American Ring Size (Ring Sizes In The United States, Canada And Mexico) to Diameter In Millimeters (mm, Inner Diameter And Circumference Of A Ring)

Ring size conversion page helps to convert jewelry ring sizes used around the globe. As you could probably expect, people use different scales to mark ring sizes in various parts of the world. This is not a problem though, our converter lets you instantly convert a ring size from any scale to all the others.

Ring sizes can be measured by inner diameter of a ring or by the length of the inner circumference of a ring.

Unlike many other ring conversion tables you can find on the web, we use formulas to calculate exact conversions based on official standards instead of providing a loose approximate matching. We want to make sure you get the most reliable conversion result.

For most systems we round up sizes to a quarter of a size step. If this rounding-up adds difference of more than 1%, we show the actual difference as a percent of the ring diameter. It may sound cumbersome, but it's easy. Just try it – enter any ring size and get it converted to all other sizes.