Ring size is a measurement used to denote the circumference (or sometimes the diameter) of jewellery rings and smart rings.
Ring sizes can be measured physically by a paper, plastic or metal ring sizer (as a gauge) or by measuring the inner diameter of a ring that already fits.
Ring sticks used to measure the inner size of a ring can be made from a variety of materials including plastic, delrin, wood, aluminium, aluminium with wooden handle and so on. Digital ring sticks also exist.
The ISO standard for ring sizes is ISO 8653:2016, which defines standard ring sizes in terms of the inner circumference of the ring measured in millimetres. ISO sizes are used in Austria, France, Germany, Belgium and Scandinavia (Norway, Sweden, Denmark, Finland, Iceland), as well as some other countries in Continental Europe.
This international standard specifies a method to measure the ring-size using a ring stick with defined characteristics, which is mainly used during manufacturing steps, and specifies the designation of the ring-size.
For jeweller-consumer relationships, the finger size is measured with a finger gauge set made up of a ring for each size with the same diameter and tolerance as the ring stick ones. The sizes are in millimeters and correspond directly to the outer circumference of the ring stick to the inner circumference of the finger gauge.
ISO sizes 49 to 60
|Internal ring circumference (mm)||49||50||51||52||53||54||55||56||57||58||59||60|
|Internal diameter (mm)||15.6||15.9||16.2||16.6||16.9||17.2||17.5||17.8||18.1||18.5||18.8||19.1|
ISO sizes 61 to 72
|Internal ring circumference (mm)||61||62||63||64||65||66||67||68||69||70||71||72|
|Internal diameter (mm)||19.4||19.7||20.1||20.4||20.7||21.0||21.3||21.6||22.0||22.3||22.6||22.9|
Other traditional and regional systems
There are several systems for denoting the sizes of jewellery rings in use around the world:
- In the United States, Canada and Mexico ring sizes are specified using a numerical scale, with quarter and half sizes. An increase of a full size is an increase of 0.032 inch (0.8128 mm) in diameter, or roughly 1/10 inch (more precisely, 0.1005 in or 2.55 mm) in inside circumference.
- In Ireland, the United Kingdom and Australia, ring sizes are specified using an alphabetical scale, with half sizes.
- In India, Japan and China, ring sizes are specified using a numerical scale, that only has whole sizes, and does not have simple linear correlation with diameter or circumference.
- In Italy, Spain, Netherlands, and Switzerland, ring sizes are specified as the circumference minus 40 mm. A 50 ISO was a 10 in Switzerland.
For the system prevailing the United States, the Circular of the Bureau of Standards summarizes the situation as: “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.” The standards are generally consistent and remain so. There does not appear to have been any improvement in the standard since then.
Ring Size Chart
|Inside diameter||Inside circumference||Sizes|
South Africa and
To convert from US, Canada and Mexico ring sizes (s) to ISO 8653:2016 circumference:
c = 2.55 x s + 36.5
and for diameter:
d = 0.8128 x s + 11.63
Resizing a ring
Most rings can have their size adjusted to some extent. There are various methods which may be suitable depending on the complexity of the ring and material used. For example, rings of soft material may be opened somewhat using a special form of punch.
In other cases the ring may need to be cut open and material either added or removed, before fusing the ring together again. All other factors being equal, sizing a ring up will cost more than sizing a ring down; sizing up requires the jeweler add precious metal, sizing down allows them to remove (and re-use) it.
Sizing beads are an alternative way to reduce the functional ring size by adding small metal beads to the inner surface of a ring, and can aid in holding the ring in place against the finger. Mounting sizing beads can be an easy way to resize a ring that is too big. They are also sometimes used on very top heavy rings as a counter balance.
Persons who have knuckles that are much larger than their finger base may also benefit from sizing beads to keep a ring from spinning. Sizing beads are typically made of the same metal as the rest of the ring, since it is easier to solder two similar metals.