Ring Size International Conversion Chart

Inside Diameter	Inside Circumference		Sizes
(in)	(in)	(mm)	Australian	British	French size	German	Italian	Japanese	Swiss	USA
1 7/8	1 8/9	48	I 1/2	I 1/2	47 3/4	15.25	8	8	8	4 1/2
1 15/16	1 15/16	49	J 1/2	J 1/2	49	15.75	9.5	9	9.25	5
2	2	51	L	L	50 1/4	16	10.5	11	11.75	5 1/2
2 1/16	2 1/16	52	M	M	51 1/2	16.5	11.5	12	12.75	6
2 1/8	2 1/16	53	N	N	52 3/4	17	13	13	14	6 1/2
2 3/16	2 1/7	55	O	O	54	17.25	14.5	14	15.25	7
2 1/4	2 1/5	56	P	P	55 1/4	17.75	16	15	16.5	7 1/2
2 5/16	2 1/4	57	Q	Q	56 1/2	18	17	16	17.75	8
2 3/8	2 2/7	58	Q 1/2	Q 1/2	57 3/4	18.5	18.5	17	18.25	8 1/2
2 7/16	2 1/3	59	R 1/2	R 1/2	59	19	19.5	18	19.5	9
2 1/2	2 2/5	61	S 1/2	S 1/2	60 1/4	19.5	21	19	20.75	9 1/2
2 9/16	2 4/9	62	T 1/2	T 1/2	61 1/2	20	22	20	22	10
2 5/8	2 1/2	63	U 1/2	U 1/2	62 3/4	20.25	23.5	22	23.25	10 1/2
2 11/16	2 1/2	65	V 1/2	V 1/2	64	20.75	25	23	24.75	11
2 3/4	2 3/5	66	W 1/2	W 1/2	65 1/2	21	26.5	24	26	11 1/2
2 13/16	2 2/3	68	Y	Y	66 1/2	21.25	27.5	25	27.5	12
2 7/8	2 5/7	69	Z	Z	67 3/4	21.75	28.5	26	28.75	12 1/2
2 15/16	2 3/4	70	Z 1	Z 1	69	22	30	27	29.75	13

Chart Key and Descriptions

Australian & British sizes = Alphabetical scale, with half sizes

French & German sizes = Measured using actual internal circumference (mm)

Italian & Swiss sizes = Measured using the circumference minus 40mm

Japanese sizes = Numerical scale, only has whole sizes, does not have a linear correlation with diameter or circumference

USA sizes = Numerical scale, with quarter and half sizes