American Standard & ISO Metric Thread Sizes& Tap Drills

*Indicates Size of drill to be used before tapping

American Standard Thread			ISO Metric Thread
Thread Size	Tap Drill Size (in.)		Thread Size	Tap Drill Size (mm)
0-80	3/64		M1 x 0.25	0.75
1-64	53		M1.1 x 0.25	0.85
1-72	53		M1.2 x 0.25	0.95
2-56	51		M1.4 x 0.3	1.10
2-64	50		M1.6 x 0.35	1.25
3-48	5/64		M1.8 x 0.35	1.45
3-56	46		M2 x 0.4	1.60
4-40	43		M2.2 x 0.45	1.75
4-48	42		M2.5 x 0.45	2.05
5-40	39		M3 x 0.5	2.50
American Standard Thread			ISO Metric Thread
Thread Size	Tap Drill Size (in.)		Thread Size	Tap Drill Size (mm)
5-44	37		M3.5 x 0.6	2.90
6-32	36		M4 x 0.7	3.30
6-40	33		M4.5 x 0.75	3.70
8-32	29		M5 x 0.8	4.20
8-36	29		M6 x 1	5.00
10-24	25		M7 x 1	6.00
10-32	21		M8 x 1.25	6.80
12-24	17		M9 x 1.25	7.80
12-28	15		M10 x 1.5	8.50
1/4-20	7		M11 x 1.5	9.50
American Standard Thread			ISO Metric Thread
Thread Size	Tap Drill Size (in.)		Thread Size	Tap Drill Size (mm)
1/4-28	3		M12 x 1.75	10.20
5/16-18	F		M14 x 2	12.00
5/16-24	I		M16 x 2	14.00
3/8-16	5/16		M18 x 2.5	15.50
3/8-24	Q		M20 x 2.5	17.50
7/16-14	U		M22 x 2.5	19.50
7/16-20	W		M24 x 3	21.00
1/2-13	27/64		M27 x 3	24.00
1/2-20	29/64		M30 x 3.5	26.50
9/16-12	31/64		M33 x 3.5	29.50
American Standard Thread			ISO Metric Thread
Thread Size	Tap Drill Size (in.)		Thread Size	Tap Drill Size (mm)
9/16-18	33/64		M36 x 4	32.00
5/8-11	17/32		M39 x 4	35.00
5/8-18	37/64		M42 x 4.5	37.50
3/4-10	21/32		M45 x 4.5	40.50
3/4-16	11/16		M48 x 5	43.00
7/8-9	49/64		M52 x 5	47.00
7/8-14	13/16		M56 x 5.5	50.50
1"-8	7/8		M60 x 5.5	54.50
1"-14	15/16		M64 x 6	58.00
			M68 x 6	62.00