Ring circumference

Ring circumference is the length around the inside of a ring, which is also the circumference of the finger it fits. Every ring size is built on it: under ISO 8653, the European size is the inner circumference in millimeters, so a 54 mm ring is an EU 54. US, UK and Japanese sizes are scales of their own on the same length.

How to measure

1. Wrap a strip of paper around the base of the finger.
2. Mark where it overlaps.
3. Lay it flat and measure the length: that is the inner circumference.
4. Measure at the end of the day. The template's note: "Fingers swell in the heat: measure at the end of the day."

On a size chart

The Rings template gives US sizes 5 to 12 with their UK and EU sizes, the inner diameter and the inner circumference. A few rows:

The template's UK and EU sizes are the engine's, which converts with the usual scales: a US size follows 2.55 mm times the size plus 36.5 mm; UK letters move one letter per 1.25 mm, with C at 40 mm.

In Ruban Size

Find my size for rings asks for the finger, or "the inner diameter of a ring that fits you", and gives the Japanese size even when the chart has no JP row. There is no "Fit I like" for rings: a ring too loose fails as surely as a ring too tight. For wide bands, a chart can be set to take the larger of two sizes, and shoppers read "Wide band: between two sizes, take the larger one."