Ring size

File:Triboulet.jpg

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

File:Ring sizer measuring tool 4.jpg

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, Nordic countries (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

File:Metal ring size set.jpg

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 1⁄4 steps, where whole sizes differ by of internal diameter, equivalent to 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 . 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:Rnd		0
0.466		Template:Rnd		1⁄4
0.474		Template:Rnd		1⁄2	A
0.482		Template:Rnd		3⁄4	A+1⁄2
0.49		Template:Rnd		1	B	1
0.498		Template:Rnd		1+1⁄4	B+1⁄2
0.506		Template:Rnd		1+1⁄2	C
0.514		Template:Rnd		1+3⁄4	C+1⁄2		1
0.522		Template:Rnd		2	D	2	2
0.53		Template:Rnd		2+1⁄4	D+1⁄2
0.538		Template:Rnd		2+1⁄2	E	3	3
0.546		Template:Rnd		2+3⁄4	E+1⁄2		4
0.554		Template:Rnd		3	F	4
0.562		Template:Rnd		3+1⁄4	F+1⁄2	5	5
0.57		Template:Rnd		3+1⁄2	G
0.578		Template:Rnd		3+3⁄4	G+1⁄2	6	6
0.586		Template:Rnd		4	H	7
0.594		Template:Rnd		4+1⁄4	H+1⁄2		7
0.602		Template:Rnd		4+1⁄2	I	8	8
0.61		Template:Rnd		4+3⁄4	J		9
0.618		Template:Rnd		5	J+1⁄2	9
0.626		Template:Rnd		5+1⁄4	K		10
0.634		Template:Rnd		5+1⁄2	K+1⁄2	10
0.642		Template:Rnd		5+3⁄4	L		11
0.65		Template:Rnd		6	L+1⁄2	11	12
0.658		Template:Rnd		6+1⁄4	M	12
0.666		Template:Rnd		6+1⁄2	M+1⁄2	13	13
0.674		Template:Rnd		6+3⁄4	N
0.682		Template:Rnd		7	N+1⁄2	14	14
0.69		Template:Rnd		7+1⁄4	O		15
0.698		Template:Rnd		7+1⁄2	O+1⁄2	15
0.706		Template:Rnd		7+3⁄4	P		16
0.714		Template:Rnd		8	P+1⁄2	16	17
0.722		Template:Rnd		8+1⁄4	P+3⁄4
0.73		Template:Rnd		8+1⁄2	Q+1⁄4	17	18
0.738		Template:Rnd		8+3⁄4	R		19
0.746		Template:Rnd		9	R+1⁄2	18
0.754		Template:Rnd		9+1⁄4	S		20
0.762		Template:Rnd		9+1⁄2	S+1⁄2	19	21
0.77		Template:Rnd		9+3⁄4	T
0.778		Template:Rnd		10	T+1⁄2	20	22
0.786		Template:Rnd		10+1⁄4	U	21	23
0.794		Template:Rnd		10+1⁄2	U+1⁄2	22
0.802		Template:Rnd		10+3⁄4	V		24
0.81		Template:Rnd		11	V+1⁄2	23	25
0.818		Template:Rnd		11+1⁄4	W
0.826		Template:Rnd		11+1⁄2	W+1⁄2	24	26
0.834		Template:Rnd		11+3⁄4	X
0.842		Template:Rnd		12	X+1⁄2	25	27
0.85		Template:Rnd		12+1⁄4	Y		28
0.858		Template:Rnd		12+1⁄2	Y+1⁄2	26
0.866		Template:Rnd		12+3⁄4	Z		29
0.874		Template:Rnd		13	Z+1⁄2	27	30
0.882		Template:Rnd		13+1⁄4	Z1
0.89		Template:Rnd		13+1⁄2			31
0.898		Template:Rnd		13+3⁄4	Z2		32
0.906		Template:Rnd		14	Z3
0.914		Template:Rnd		14+1⁄4			33
0.922		Template:Rnd		14+1⁄2	Z4
0.93		Template:Rnd		14+3⁄4			34
0.938		Template:Rnd		15			35
0.946		Template:Rnd		15+1⁄4
0.954		Template:Rnd		15+1⁄2			36
0.962		Template:Rnd		15+3⁄4
0.97		Template:Rnd		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.