Japan · 27 sizes

Japan / China Ring Size Chart.

Numeric scale, roughly 1 to 27. Also used in much of East Asia.

Every row is computed from inner circumference, so the diameter and the equivalents in other systems are consistent all the way down.

Japan / China	Diameter	Circumference	Indian	US / Canada	EU / ISO 8653	UK / Australia	Swiss
1	12.99 mm	40.8 mm	—	—	—	D	1
2	13.28 mm	41.7 mm	1	—	—	D½	2
3	13.58 mm	42.7 mm	2	—	—	E½	3
4	13.87 mm	43.6 mm	3	3	44	F	4
5	14.16 mm	44.5 mm	4	3	44	G	4
6	14.45 mm	45.4 mm	5	3½	45	G½	5
7	14.74 mm	46.3 mm	6	4	46	H	6
8	15.04 mm	47.2 mm	7	4	47	I	7
9	15.33 mm	48.2 mm	8	4½	48	I½	8
10	15.62 mm	49.1 mm	9	5	49	J½	9
11	15.91 mm	50.0 mm	10	5½	50	K	10
12	16.20 mm	50.9 mm	11	5½	51	L	11
13	16.50 mm	51.8 mm	12	6	52	L½	12
14	16.79 mm	52.7 mm	13	6½	53	M	13
15	17.08 mm	53.7 mm	14	6½	54	N	14
16	17.37 mm	54.6 mm	15	7	55	N½	15
17	17.66 mm	55.5 mm	16	7½	55	O½	15
18	17.95 mm	56.4 mm	17	8	56	P	16
19	18.25 mm	57.3 mm	19	8	57	Q	17
20	18.54 mm	58.2 mm	20	8½	58	Q½	18
21	18.83 mm	59.2 mm	21	9	59	R½	19
22	19.12 mm	60.1 mm	22	9	60	S	20
23	19.41 mm	61.0 mm	23	9½	61	S½	21
24	19.71 mm	61.9 mm	24	10	62	T½	22
25	20.00 mm	62.8 mm	25	10½	63	U	23
26	20.29 mm	63.7 mm	26	10½	64	V	24
27	20.58 mm	64.7 mm	27	11	65	V½	25

Convert Japan / China to another system

A jeweller's own chart takes precedence over this one — makers differ by a fraction of a size and a proper mandrel beats a paper strip. Fingers also swell through the day and in heat, so measure in the evening. How to measure at home →