Ring size

Ring sticks are tools used to measure the inner size of a ring, and are typically made from plastic, delrin, wood, aluminium, or of multiple materials.

Digital ring sticks can be used for highly accurate measurements.

[1] ISO sizes are used in Austria, France, Belgium, Scandinavia (Norway,[2] Sweden, Denmark, Finland, Iceland), and other countries in Continental Europe.

[3][4] Other ring size measurement systems are used in areas that do not use ISO 8653:2016.

In the United States, Canada, and Mexico, ring sizes are specified using a numerical scale with 1⁄4 steps, where whole sizes differ by 0.032 inches (0.81 mm) of internal diameter, equivalent to 0.1005 inches (2.55 mm) of internal circumference.

The Circular of the Bureau of Standards[5] summarizes the situation with this system: "While there apparently is only one standard in use in the United States, in reality, because of the lack of specific dimensions and because of the errors introduced by the adoption of a common commercial article as a pattern, there are many, although similar, standards."

Originally in 1945, the divisions were based on the ring inside diameter in steps of 1⁄64 inch (0.40 mm).

[6] However, in 1987 BSI updated the standard to the metric system so that one alphabetical size division equals 1.25 mm of circumferential length.

Rings of soft material may be enlarged using mechanical stretching.