International Ring Size Conversion Table

US & Canada	Diameter (inch)	Diameter (mm)	Metric (mm)	British	French	German	Japanese	Swiss
0	0.39	9.91		-
00	0.422	10.72		-
000	0.454	11.53		-
1/4	0.474	11.95		A
3/4	0.482	12.18		A 1/2
1	0.487	12.37	38.9	B			1
1 1/4	-	12.6	39.6	B 1/2
1 1/2	0.503	12.78	40.2	C
1 3/4	-	13	40.8	C 1/2
2	0.52	13.21	41.5	D	41 1/2	13 1/2	2	1 1/2
2 1/4	-	13.41	42.1	D 1/2	-	-
2 1/2	0.536	13.61	42.7	E	42 3/4	13 3/4	3	2 3/4
2 3/4	-	13.83	43.4	E 1/2	-	-
3	0.553	14.05	44	F	44	14	4	4
3 1/8	-	14.15	44.3	F 1/2	-	-
3 1/4	-	14.25	44.6	-	-	-
3 3/8	-	14.36	44.9	G	45 1/4	-	5	5 1/4
3 1/2	0.569	14.45	45.2	-	-	14 1/2
3 5/8	-	14.56	45.6	G 1/2	-		6
3 3/4	-	14.65	45.9	H	46 1/2			6 1/2
4	0.585	14.86	46.5	H 1/2	-	15	7
4 1/4	-	15.04	47.1	I	47 3/4			7 3/4
4 1/2	0.601	15.27	47.8	I 1/2	-	15 1/4	8
4 5/8	-	15.4	48.1	J	49	15 1/2		9
4 3/4	-	15.53	48.4	-	-
5	0.618	15.7	49	J 1/2	-	15 3/4	9
5 1/8	-	15.8	49.3	K	50			10
5 1/4	-	15.9	49.6	-	-
5 3/8	-	16	50	K 1/2	-		10
5 1/2	0.634	16.1	50.3	L	51 3/4	16		11 3/4
5 3/4	-	16.3	50.9	-	-
5 7/8	-	16.41	51.3	L 1/2	-
6	0.65	16.51	51.5	M	52 3/4	16 1/2	12	12 3/4
6 1/4	-	16.71	52.2	M 1/2	-
6 1/2	0.666	16.92	52.8	N	54	17	13	14
6 3/4	-	17.13	53.4	N 1/2	-
7	0.683	17.35	54	O	55 1/4	17 1/4	14	15 1/4
7 1/4	-	17.45	54.7	O 1/2	-
7 1/2	0.699	17.75	55.3	P	56 1/2	17 3/4	15	16 1/2
7 3/4	-	17.97	55.9	P 1/2	-
8	0.716	18.19	56.6	Q	57 3/4	18	16	17 3/4
8 1/4	-	18.35	57.2	Q 1/2	-
8 1/2	0.732	18.53	57.8	-	-	18 1/2	17
8 5/8	-	18.61	58.4	R	59			19
8 3/4	-	18.69	58.4	-	-
8 7/8	-	18.8	59	R 1/2	-
9	0.748	18.89	59.1	-	-	19	18
9 1/8	-	19.1	59.4	S	60 1/4			20 1/4
9 1/4	-	19.22	59.7	-	-
9 3/8	-	19.31	60	S 1/2	-
9 1/2	0.764	19.41	60.3	-	-	19 1/2	19
9 5/8	-	19.51	60.6	T	61 1/2			21 1/2
9 3/4	-	19.62	60.9	-	-
10	0.781	19.84	61.6	T 1/2	-	20	20
10 1/4	-	20.02	62.2	U	62 3/4		21	22 3/4
10 1/2	0.797	20.2	62.8	U 1/2	-	20 1/4	22
10 5/8	-	20.32	63.1	V	63			23 3/4
10 3/4	-	20.44	63.5	-	-
11	0.814	20.68	64.1	V 1/2	-	20 3/4	23
11 1/8	-	20.76	64.3	W	65			25
11 1/4	-	20.85	64.7	-	-
11 3/8	-	20.94	65	W 1/2	-
11 1/2	-	21.08	65.3	-	-	21	24
11 5/8	0.83	21.18	65.7	X	66 1/4			26 1/4
11 3/4	-	21.24	66	-	-
11 7/8	-	21.3	66.3	X 1/2	-
12	0.846	21.49	66.6	Y	67 1/2	21 1/4	25	27 1/2
12 1/4	-	21.69	67.2	Y 1/2	-
12 1/2	0.862	21.89	67.9	Z	68 3/4	21 3/4	26	28 3/4
12 3/4	-	22.1	68.5	Z 1/2	-
13	0.879	22.33	69.1	-	-	22	27

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International Ring Size Conversion Table

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