Inside Diameter (inches)	Inside Diameter (mm)	Inside Circumference (inches)	Inside Circumference (mm)	Number Sizes US/Canada (standard)	Wheat Sheaf, British, Irish, Austrailian Equivalent	Japanese Equivalent	Swiss Equivalent
0.586	14.9	1.840	46.7	4	H	7
0.602	15.3	1.890	48.0	4 1/2	I	8
0.618	15.7	1.941	49.3	5	J 1/2	9
0.634	16.1	1.991	50.6	5 1/2	K 1/2	10
0.650	16.5	2.041	51.8	6	L 1/2	11	12.75
0.666	16.9	2.091	53.1	6 1/2	M 1/2	13	14.00
0.682	17.3	2.141	54.4	7	N 1/2	14	15.25
0.698	17.7	2.192	55.7	7 1/2	O 1/2	15	16.50
0.714	18.1	2.242	56.9	8	P 1/2	16	17.75
0.730	18.5	2.292	58.2	8 1/2	Q 1/2	17
0.746	18.9	2.342	59.5	9	R 1/2	18
0.762	19.4	2.393	60.8	9 1/2	S 1/2	19
0.778	19.8	2.443	62.1	10	T 1/2	20
0.794	20.2	2.493	63.3	10 1/2	U 1/2	22	22.75
0.810	20.6	2.543	64.6	11	V 1/2	23
0.826	21.0	2.594	65.9	11 1/2	W 1/2	24
0.842	21.4	2.644	67.2	12	X 1/2	25	27.50
0.858	21.8	2.694	68.4	12 1/2	Z	26	28.75
0.874	22.2	2.744	69.7	13		27
0.890	22.6	2.795	71.0	13 1/2
0.906	23.0	2.845	72.3	14	Z3
0.922	23.4	2.895	73.5	14 1/2	Z4
0.938	23.8	2.945	74.8	15
0.954	24.2	2.996	76.1	15 1/2