Drill sizes for taps

| Standard Taps | Metric Taps | Pipe Taps |

Recommended sizes for standard taps.

Tap Size and TPI	Recommended Drill Size		Tap Size and TPI	Recommended Drill Size		Tap Size and TPI	Recommended Drill Size
#0-80	3/64		1/4-20	#7		1-8	7/8
#1-64	#53		1/4-28	#3		1-12	59/64
#1-72	#53		5/16-18	F		1-14	15/16
#2-56	#50		5/16-24	I		1 1/8-7	63/64
#2-64	#50		3/8-16	5/16		1 1/8-12	1 3/64
#3-48	#47		3/8-24	Q		1 1/4-7	1 7/64
#3-56	#46		7/16-14	U		1 1/4-12	1 11/64
#4-40	#43		7/16-20	25/64		1 1/2-6	1 11/32
#4-48	#42		1/2-12	27/64		1 1/2-12	1 27/64
#5-40	#38		1/2-13	27/64		1 3/4-5	1 35/64
#5-44	#37		1/2-20	29/64		1 3/4-12	1 43/64
#6-32	#36		9/16-12	31/64		2-4 1/2	1 25/32
#6-40	#33		9/16-18	33/64		2-12	1 59/64
#8-32	#29		5/8-11	17/32		2 1/4-4 1/2	2 1/32
#8-36	#29		5/8-18	37/64		2 1/2-4	2 1/4
#10-24	#25		3/4-10	21/32		2 3/4-4	2 1/2
#10-32	#21		3/4-16	11/16		3-4	2 3/4
#12-24	#16		7/8-9	49/64
#12-28	#14		7/8-14	13/16

Recommended drill sizes for metric taps.

Tap Size	Recommended Drill Size (mm)		Tap Size	Recommended Drill Size (mm)
M1.6-0.35	1.25		M12-1.75	10.2
M1.8-0.35	1.45		M12-1.25	10.8
M2-0.4	1.6		M14-2.0	12
M2.2-0.45	1.75		M14-1.5	12.5
M2.5-.045	2.05		M16-2.0	14
M3-0.5	2.5		M16-1.5	14.5
M3.5-0.6	2.9		M18-2.5	15.5
M4-0.7	3.3		M18-1.5	16.5
M4.5-0.75	3.7		M20-2.5	17.5
M5-0.8	4.2		M20-1.5	18.5
M6-1.0	5		M22-2.5	19.5
M7-1.0	6		M22-1.5	20.5
M8-1.25	6.7		M24-3.0	21
M8-1.0	7		M24-2.0	22
M10-1.5	8.5		M27-3.0	24
M10-1.25	8.7		M27-2.0	25

Recommended drill sizes for pipe taps.

Tap Size	Recommended Taper pipe Drill Size	Recommended Straight pipe Drill Size
1/16-27	D	1/4
1/8-27	Q	S
1/4-18	7/16	29/64
3/8-18	9/16	19/32
1/2-14	45/64	47/64
3/4-14	29/32	15/16
1-11 1/2	1 9/64	1 3/16
1 1/4-11 1/2	1 31/64	1 33/64
1 1/2-11 1/2	1 47/64	1 3/4
2-11 1/2	2 13/64	2 7/32
2 1/2-8	2 5/8	2 21/32
3-8	3 1/4	3 9/32
3 1/2-8	3 3/4	3 25/32
4-8	4 1/4	4 9/32
5-8	5 9/32	5 11/32
6-8	6 11/32	6 13/32