ALLIANCES & JONCS

There are several systems for denoting the sizes of jewellery rings in use around the world^[1]:

In the United States and Canada, 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 roughly¹/₁₀ inch (more precisely, 0.1005 in or 2.55 mm) in inside circumference.

Generally, sizes in quarters and halves will not relate conventionally to anything on any known ruler. Also, on one finger alone a person may vary more than a whole ring size- depending on time of day, work performed, and other swelling-inducing activities/conditions. Therefore, in most cases quarter-sizes are meaningless unless one needs precise accuracy with a particular ring.

In Europe (excluding Ireland and the United Kingdom), ring sizes are specified using a numerical scale, with half sizes.
In Ireland, the United Kingdom and Australia, ring sizes are specified using an alphabetical scale, with half sizes.
In Japan, ring sizes are specified using a numerical scale, that only has whole sizes.
In Switzerland, ring sizes are specified using a numerical scale, with quarter and half sizes.
In Germany, ring sizes are specified using actual internal circumference in mm. (the same as ISO)

The ISO standard for ring sizes is ISO 8653:1986, which defines standard ring sizes in terms of the inner circumference of the ring measured in millimetres.

[edit]Conversion chart for ring sizes

Inside diameter		Inside circumference		Sizes
(in)	(mm)	(in)	(mm)	United States and Canada	United Kingdom, Ireland, and Australia	Japan, China	Switzerland
0.459	11.63	1.44	36.5	0
0.466	11.84	1.46	37.2	¼
0.474	12.04	1.49	37.8	½	A
0.482	12.24	1.51	38.5	¾	A½
0.49	12.45	1.54	39.1	1	B	1
0.498	12.65	1.56	39.7	1¼	B½
0.506	12.85	1.59	40.4	1½	C
0.514	13.06	1.61	41.0	1¾	C½
0.522	13.26	1.64	41.7	2	D	2	1.5
0.53	13.46	1.67	42.3	2¼	D½
0.538	13.67	1.69	42.9	2½	E	3	2.75
0.546	13.87	1.72	43.6	2¾	E½
0.554	14.07	1.74	44.2	3	F	4	4
0.562	14.27	1.77	44.8	3¼	F½	5	5.25
0.57	14.48	1.79	45.5	3½	G
0.578	14.68	1.82	46.1	3¾	G½	6	6.5
0.586	14.88	1.84	46.8	4	H	7
0.594	15.09	1.87	47.4	4¼	H½		7.75
0.602	15.29	1.89	48.0	4½	I	8
0.61	15.49	1.92	48.7	4¾	J		9
0.618	15.70	1.94	49.3	5	J½	9
0.626	15.90	1.97	50.0	5¼	K		10
0.634	16.10	1.99	50.6	5½	K½	10
0.642	16.31	2.02	51.2	5¾	L		11.75
0.65	16.51	2.04	51.9	6	L½	11	12.75
0.658	16.71	2.07	52.5	6¼	M	12
0.666	16.92	2.09	53.1	6½	M½	13	14
0.674	17.12	2.12	53.8	6¾	N
0.682	17.32	2.14	54.4	7	N½	14	15.25
0.69	17.53	2.17	55.1	7¼	O
0.698	17.73	2.19	55.7	7½	O½	15	16.5
0.706	17.93	2.22	56.3	7¾	P
0.714	18.14	2.24	57.0	8	P½	16	17.75
0.722	18.34	2.27	57.6	8¼	Q
0.73	18.54	2.29	58.3	8½	Q½	17
0.738	18.75	2.32	58.9	8¾	R		19
0.746	18.95	2.34	59.5	9	R½	18
0.754	19.15	2.37	60.2	9¼	S		20.25
0.762	19.35	2.39	60.8	9½	S½	19
0.77	19.56	2.42	61.4	9¾	T		21.5
0.778	19.76	2.44	62.1	10	T½	20
0.786	19.96	2.47	62.7	10¼	U	21
0.794	20.17	2.49	63.4	10½	U½	22	22.75
0.802	20.37	2.52	64.0	10¾	V
0.81	20.57	2.54	64.6	11	V½	23
0.818	20.78	2.57	65.3	11¼	W		25
0.826	20.98	2.59	65.9	11½	W½	24
0.834	21.18	2.62	66.6	11¾	X
0.842	21.39	2.65	67.2	12	X½	25	27.5
0.85	21.59	2.67	67.8	12¼	Y
0.858	21.79	2.70	68.5	12½	Z	26	28.75
0.866	22.00	2.72	69.1	12¾	Z½
0.874	22.20	2.75	69.7	13		27
0.882	22.40	2.77	70.4	13¼	Z1
0.89	22.61	2.80	71.0	13½
0.898	22.81	2.82	71.7	13¾	Z2
0.906	23.01	2.85	72.3	14	Z3
0.914	23.22	2.87	72.9	14¼
0.922	23.42	2.90	73.6	14½	Z4
0.93	23.62	2.92	74.2	14¾
0.938	23.83	2.95	74.8	15
0.946	24.03	2.97	75.5	15¼
0.954	24.23	3.00	76.1	15½
0.962	24.43	3.02	76.8	15¾
0.97	24.64	3.05	77.4	16

[edit]Finger sizing

Ring size is not the same as finger size. A professional jeweler can determine proper ring size using a set of steel gauge-rings. These "ring sizers" come in narrow and wide widths. Fingers change over the course of the day due to diet or work affecting the results using gauge rings.

Other methods, such as measuring the finger with a strip of paper, or slipping the finger through pre-cut "measuring holes", are inaccurate. It has been recommended that fingers be measured at the end of the day, when they are at their largest diameters. Existing fitted rings can also be measured for increased accuracy. Other factors that can affect ring size include: the menstrual cycle, temperature, humidity, water-retention and exercise.

The best strategy for measurement is to purchase calipers that measure inside diameters. A tightly-calipered measurement should then be taken of various rings that fit; these should be noted and the corresponding size recorded. The MANDREL, the tapered ring-measuring rod, should be regarded as only half-accurate. Different jewelers will employ the mandrel in different ways. For instance, one jeweler may use the mandrel and take an edge-of-the-ring reading; others will take the measure that corresponds to the largest finger the ring can fit.

It is best for the consumer to know and be firm about finger dimensions, because every jeweler or ring seller will think his/her method is the "best" ring-measuring method. It has often been suggested that the industry universally standardize on using inner diameter (the diameter of the finger) as the only size-number method of determination.

A wider band can be worn more loosely. Large knuckles/hands should wear a slightly loose ring, while slimmer knuckles/smaller hands will require a tighter ring. Some rings can be re-sized, but many cannot. Rings made of titanium or tungsten steel, stone-set rings with complicated or precise mountings, extremely thin/wide rings cannot be re-sized.

A good way for a "rough-and-ready" measurement is to find a ring that is just smaller than the second knuckle of the finger. This way the fit is comfortable but will not slide off the finger. The method of trying on a ring and shaking the hand violently, to see if the ring comes off, is inadvisable and not very accurate.

Furthermore, every ring size chart will vary slightly in its standards. This always occurs unless one company has copied another company's size chart. Even the ISO, ringsmiths and jewelers use different sizing standards, assigning different numbers to the same measurements. On one chart a diameter of 20.65mm may equal a size 10 3/4; on another chart, a similar number, such as 20.62mm, may read out as size 10. It is wise to keep all of the above firmly in mind when ring shopping.

If ordering from catalog or internet, always demand that the seller provide the inner diameter of a ring.