American National Standard (U.S. Customary Units)
TAP SIZE	TAP DRILL SIZE	M/M	DECIMAL EQUIV. OF TAP DRILL (INCHES)	PROBABLE % OF THREAD
0-80	56		0.0465	74
	3/64	1.20	0.0469	72
1-64	54	1.40	0.0550	81
	53	1.50	0.0595	59
1-72	53	1.50	0.0595	67
	1/16		0.0625	50
2-56	51		0.0670	75
	50	1.75	0.0700	62
2-64	50	1.80	0.0700	71
	49		0.0730	56
3-48	48	2.00	0.0760	79
	5/64		0.0781	71
3-56	46	2.10	0.0810	71
	45		0.0820	66
4-40	44		0.0860	75
	43	2.25	0.0890	66
	42		0.0935	51
	3/32		0.0938	50
4-48	42	2.35	0.0935	62
	3/32		0.0938	60
5-40	39		0.0995	73
	38	2.60	0.1015	67
5-44	38		0.1015	74
	37	2.60	0.1040	65
6-32	36	2.70	0.1065	73
	7/64		0.1095	66
6-40	33	2.90	0.1130	72
	32		0.1160	62
8-32	29	3.40	0.1360	64
8-36	29	3.54	0.1350	72
	9/64		0.1406	60
10-24	25	3.80	0.1495	71
10-32	5/32		0.1563	78
	21	4.00	0.1590	72
12-34	11/64		0.1719	78
	17	4.50	0.1730	76
12-28	16		0.1770	80
	15	4.60	0.1800	73
1/4-20	9		0.1960	80
	7	5.10	0.2010	72
	13/64		0.2031	69
1/4-28	3		0.2130	75
	7/32	5.50	0.2188	59
5/16-18	F	6.50	0.2570	74
	G		0.2610	68
5/16-24	H		0.2660	78
	I	6.90	0.2720	70
3/8-16	5/16	8.00	0.3125	74
	O		0.3160	69
3/8-24	Q	8.50	0.3320	75
	R		0.3390	58
7/16-14	23/64	9.30	0.3594	81
	U		0.3680	70
7/16-20	W		0.3860	75
	25/64	9.90	0.3906	68
1/2-13	27/64	10.75	0.4219	75
	7/16		0.4375	58
1/2-20	29/64	11.50	0.4531	67
9/16-12	15/32		0.4688	84
	31/64	12.00	0.4844	69
9/16-18	1/2		0.5000	82
	33/64	13.00	0.5156	60
5/8-11	17/32	13.50	0.5313	76
	35/64		0.5469	63
5/8-18	9/16		0.5625	82
	37/64	14.50	0.5781	60
3/4-10	41/64		0.6406	81
	21/32	16.50	0.6563	69
3/4-16	11/16	17.50	0.6875	72
7/8-9	49/64	18.50	0.7656	73
	25/32		0.7813	62
7/8-14	51/64		0.7969	79
	13/16	20.50	0.8125	62
1-8	7/8	22.50	0.8750	74
	57/64		0.8906	64
1-12	29/32		0.9063	82
	59/64	23.50	0.9219	68
1-14	59/64		0.9219	79
	15/16	23.50	0.9375	62
1-1/8-7	63/64	25.00	0.9844	73
	1		1.0000	65
1-1/8-12	1-1/32		1.0313	82
	1-3/64	26.50	1.0469	67
1-1/4-7	1-3/32		1.0938	81
	1-7/64	28.00	1.1094	73
	1-1/8		1.1250	64
1-1/4-12	1-5/32		1.1563	81
	1-11/64	29.50	1.1719	67
1-3/8-6	1-13-64		1.2031	77
	1-7/32	31.00	1.2188	69
	1-15/64		1.2344	62
1-3/8-12	1-9/32		1.2813	81
	1-19/64	33.00	1.2969	66
1-1/2-6	1-11/32	34.00	1.3438	69
	1-23/64		1.3594	62
1/1/2-12	1-13/32		1.4063	80
	1-27/64	36.00	1.4219	66