Compliments of
The International Gem Society

US Standard (Also Canada)	Diameter in Inches	British Equivalent	French Equivalent	German Equivalent	Swiss Equivalent	Japanese Equivalent
0	.454	-	-	-	-	-
1/2	-	A	-	-	-	-
1	.487	B	-	-	-	1
1 1/2	.503	C	-	-	-	-
2	.520	D	41 ½	13 ¼	1 ½	2
2 1/2	.536	E	42 ¾	13 ¾	2 ¾	3
3	.553	F	44	14	4	4
3 3/8	-	G	45 ½	-	5 ½	5
3 1/2	.569	-	-	14 ½	-	-
3 3/4	-	H	46 ½	-	6 ½	-
4	.585	H ½	-	15	-	7
4 1/4	-	I	47 ¾	-	7 ¾	-
4 7/8	-	J	49	-	9	-
5	.618	J ½	-	15 ¾	-	9
5 1/8	-	K	50	-	10	-
5 1/2	.634	L	51 ¾	16	11 ¾	-
6	.650	M	52 ¾	16 ½	12 ¾	12
6 1/2	.666	N	54	17	14	13
7	.683	O	55 ¼	17 ¼	15 ¼	14
7 1/4	.699	P	56 ½	17 ¾	16 ½	15
8	.716	Q	57 ¾	18	17 ¾	16
8 1/2	.732	-	-	18 ½	-	17
8 5/8	-	R	59	-	19	-
9	.748	-	-	19	-	18
9 1/8	-	S	60 ¼	-	20 ¼	-
9 1/4	.764	-	-	19 ½	-	19
9 5/8	-	T	61 ½	-	21 ½	-
10	.781	T ½	-	20	-	20
10 1/4	-	U	62 ¾	-	22 ¾	21
10 1/2	.797	U ½	-	20 ¼	-	22
10 5/8	-	V	63 ¾	-	23 ¾	-
11	.814	V ½	-	20 ¾	-	23
11 1/8	-	W	65	-	25	-
11 1/2	.830	-	-	21	-	24
11 5/8	-	X	66 ¼	-	26 ¼	-
12	.846	Y	67 ½	21 ¼	27 ½	25
12 1/2	.862	Z	68 ¾	21 ¾	28 ¾	26
13	.879	-	-	22	-	27

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