Ring size international comparison

ISO (International Organization for Standardization): International standardization and unification of ISO 8653, a ring size standard that differs from country to country.

ISO-8653	Japan and USA, UK, Hong Kong comparison
	Japan	Diameter(mm)	Inner circumference(mm)	USA	UK	Hong Kong
41	1	13	40.8	1	C
42	2	13.3	41.9	2	D
43	3	13.7	42.9	2.5	E
44	Four	14	44.0	3	F	6
45	Five	14.3	45.0			7
46	6	14.7	46.1	3.5	G	8
47	7	15	47.1	Four	H	9
48	8	15.3	48.2	4.5	I	Ten
49	9	15.7	49.2	Five	J	11
50	Ten	16	50.3	5.5	K	12
51	11	16.3	51.3	6	L	13
52	12	16.7	52.4	6.5	M	14
53	13	17	53.4	7	N	15
54	14	17.3	54.5	7.5	O	16
55	15	17.7	55.5	8	P	17
56	16	18	56.6			18
57	17	18.3	57.6	8.5	Q	19
58	18	18.7	58.6	9	R	20
59	19	19	59.7	9.5	S	twenty one
60	20	19.3	60.7			twenty two
61	twenty one	19.7	61.8	Ten	T	twenty three
62	twenty two	20	62.8	10.5	U	twenty four
63	twenty three	20.3	63.9	11	V	twenty five
64	twenty four	20.7	64.9	11.5	W	26
65	twenty five	twenty one	66.0	12	X	27
66	26	21.3	67.0	12.5	Y	28
67	27	21.7	68.0	13	Z	29