TABLE OF INTERNATIONAL EQUIVALENCES FOR RINGS SIZES

					Inside diameter (mm)	Inside diameter (Inches)	Inside Circumference (Inches)
48	4 1/2	I	8		15.3	0.602	1.89
48.7	4 3/4	J		9	15.5	0.61	1.915
49.3	5	J 1/2	9		15.7	0.618	1.941
49.9	5 1/4	K		10	15.9	0.626	1.966
50.6	5 1/2	K 1/2	10		16.1	0.634	1.991
51.2	5 3/4	L		11.75	16.3	0.642	2.016
51.8	6	L 1/2	11	12.75	16.5	0.65	2.041
52.5	6 1/4	M	12		16.7	0.658	2.066
53.1	6 1/2	M 1/2	13	14	16.9	0.666	2.091
53.8	6 3/4	N			17.1	0.674	2.116
54.4	7	N 1/2	14	15.25	17.3	0.682	2.141
55	7 1/4	O			17.5	0.69	2.167
55.7	7 1/2	O 1/2	15	16.5	17.7	0.698	2.192
56.3	7 3/4	P			17.9	0.706	2.217
56.9	8	P 1/2	16	17.75	18.1	0.714	2.242
57.6	8 1/4	Q			18.3	0.722	2.267
58.2	8 1/2	Q 1/2	17		18.5	0.73	2.292
58.9	8 3/4	R		19	18.7	0.738	2.317
59.5	9	R 1/2	18		18.9	0.746	2.342
60.1	9 1/4	S		20.25	19.2	0.754	2.368
60.8	9 1/2	S 1/2	19		19.4	0.762	2.393
61.4	9 3/4	T		21.5	19.6	0.770	2.418
62.1	10	T 1/2	20		19.8	0.778	2.443
62.7	10 1/4	U	21		20.0	0.786	2.468
63.3	10 1/2	U 1/2	22	22.75	20.2	0.794	2.493
64.0	10 3/4	V			20.4	0.802	2.518

Infos