Ring size

An analogic sizing ring stick

Ring size is a measurement used to denote the circumference (or sometimes the diameter) of jewellery rings and smart rings.

Measuring tools

Plastic ring sizer tool for measuring the circumference of a finger in millimeters.

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 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.

Measurement systems

International standard

ISO 8653:2016 defines standard ring sizes in terms of the inner circumference of the ring measured in millimetres. ISO sizes are used in Austria, France, Belgium, Scandinavia (Norway, Sweden, Denmark, Finland, Iceland), and other countries in Continental Europe.

Relationship between ISO size and internal diameter

ISO size (internal ring circumference, mm)	49	50	51	52	53	54	55	56	57	58	59	60	61	62	63	64	65	66	67	68	69	70	71	72
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	19.4	19.7	20.1	20.4	20.7	21	21.3	21.6	22	22.3	22.6	22.9

Other traditional and regional systems

Metal ring size set for measuring fingers.

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

North America

In the United States, Canada, and Mexico, ring sizes are specified using a numerical scale with Template:Frac steps, where whole sizes differ by Template:Convert of internal diameter, equivalent to Template:Convert of internal circumference. The relationship of this size ($s_{NA}$) to ISO 8653:2016 circumference ($C_{ISO}$) is $C_{ISO}=2.55\times s_{NA}+36.5$, while the relationship to ISO 8653:2016 diameter ($d_{ISO}$) is $d_{ISO}=0.8128\times s_{NA}+11.63$.

The Circular of the Bureau of Standards 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." The standards are generally consistent and remain so. There does not appear to have been any improvement in the standard since then.

Ireland, United Kingdom, Australia

In Ireland, the United Kingdom and Australia, ring sizes are specified using an alphabetical scale with half sizes. Originally in 1945, the divisions were based on the ring inside diameter in steps of Template:Convert. However, in 1987 BSI updated the standard to the metric system so that one alphabetical size division equals 1.25 mm of circumferential length. For a baseline, ring size C has a circumference of 40 mm.

India, Japan, China

In India, Japan and China, ring sizes are specified using a numerical scale with whole sizes that do not have a linear correlation with diameter or circumference.

Germany and Netherlands

Netherlands, Germany, and sometimes Argentina use a standard (referred to as the German System) where ring sizes are defined by the diameter of the ring, measured in mm. This system may also be used at times in Russia.

Italy, Spain, Switzerland

In Italy, Spain, and Switzerland, ring sizes are specified as the circumference minus 40 mm: for example, size 10 in this system is equivalent to ISO 8653:2016 size 50. This may also be referred to as the Swiss Ring Size System.

Russia

In Russia, ring sizes are equal to the inner diameter rounded to whole and half numbers, sometimes to quarters, for example diameter 16.92 mm is equal to size 17, 16.1 mm is equal to size 16.

Equivalency table

Ring dimensions in various ring size measurement systems

Inside diameter		Inside circumference		Sizes
(in)	(mm)	(in)	(mm) ISO (Continental Europe)	United States, Canada and Mexico	United Kingdom, Ireland, Australia, South Africa and New Zealand	East Asia (China, Japan, South Korea), South America	India	Italy, Spain, Netherlands, Switzerland
0.458	Template:Convert	Template:Rnd	Template:Convert	0
0.466	Template:Convert	Template:Rnd	Template:Convert	Template:Frac
0.474	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	A
0.482	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac
0.49	Template:Convert	Template:Rnd	Template:Convert	1	B	1
0.498	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac
0.506	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	C
0.514	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac		1
0.522	Template:Convert	Template:Rnd	Template:Convert	2	D	2	2
0.53	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac
0.538	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	E	3	3
0.546	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac		4
0.554	Template:Convert	Template:Rnd	Template:Convert	3	F	4
0.562	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac	5	5
0.57	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	G
0.578	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac	6	6
0.586	Template:Convert	Template:Rnd	Template:Convert	4	H	7
0.594	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac		7
0.602	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	I	8	8
0.61	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	J		9
0.618	Template:Convert	Template:Rnd	Template:Convert	5	Template:Frac	9
0.626	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	K		10
0.634	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac	10
0.642	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	L		11
0.65	Template:Convert	Template:Rnd	Template:Convert	6	Template:Frac	11	12
0.658	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	M	12
0.666	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac	13	13
0.674	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	N
0.682	Template:Convert	Template:Rnd	Template:Convert	7	Template:Frac	14	14
0.69	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	O		15
0.698	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac	15
0.706	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	P		16
0.714	Template:Convert	Template:Rnd	Template:Convert	8	Template:Frac	16	17
0.722	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac
0.73	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac	17	18
0.738	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	R		19
0.746	Template:Convert	Template:Rnd	Template:Convert	9	Template:Frac	18
0.754	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	S		20
0.762	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac	19	21
0.77	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	T
0.778	Template:Convert	Template:Rnd	Template:Convert	10	Template:Frac	20	22
0.786	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	U	21	23
0.794	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac	22
0.802	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	V		24
0.81	Template:Convert	Template:Rnd	Template:Convert	11	Template:Frac	23	25
0.818	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	W
0.826	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac	24	26
0.834	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	X
0.842	Template:Convert	Template:Rnd	Template:Convert	12	Template:Frac	25	27
0.85	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Y		28
0.858	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Template:Frac	26
0.866	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Z		29
0.874	Template:Convert	Template:Rnd	Template:Convert	13	Template:Frac	27	30
0.882	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Z1
0.89	Template:Convert	Template:Rnd	Template:Convert	Template:Frac			31
0.898	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Z2		32
0.906	Template:Convert	Template:Rnd	Template:Convert	14	Z3
0.914	Template:Convert	Template:Rnd	Template:Convert	Template:Frac			33
0.922	Template:Convert	Template:Rnd	Template:Convert	Template:Frac	Z4
0.93	Template:Convert	Template:Rnd	Template:Convert	Template:Frac			34
0.938	Template:Convert	Template:Rnd	Template:Convert	15			35
0.946	Template:Convert	Template:Rnd	Template:Convert	Template:Frac
0.954	Template:Convert	Template:Rnd	Template:Convert	Template:Frac			36
0.962	Template:Convert	Template:Rnd	Template:Convert	Template:Frac
0.97	Template:Convert	Template:Rnd	Template:Convert	16			37

Resizing

Most rings can be resized; the method of doing so depends on the complexity of the ring and its material. Rings of soft material may be enlarged using mechanical stretching. For example, the ring may be enlarged using a rolling mill, a steel ring mandrel, or a Schwann Ring Stretcher.

Adding Material

In some cases, the ring may need to be cut open and material either added or removed before fusing the ring together again. The ring may be slightly heated to reveal any solder line so the jeweler can open the ring on the same seam so as to minimize the total number of solder joins on the ring.

Sizing beads

Small metal beads called sizing beads can be added to the inner circumference of a ring to:

• Decrease the effective inner diameter of a ring that is too big, to aid in holding the ring in place against the finger
• Counterbalance top-heavy rings
• Keep a ring from spinning for wearers whose knuckles are much larger than their finger base

Sizing beads are typically made of the same metal as the rest of the ring since it is easier to solder two similar metals.