Drill Size Chart: Fractions, Numbers, Letters and mm

A drill size chart lists every fractional, number and letter drill with its diameter in inches and millimetres. Looking for the drill to use before tapping a thread? Use the tap drill calculator.

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Fractional drills, 1/64 in to 1 in

Drill	Inches	Millimetres
1/64 in	0.0156	0.40
1/32 in	0.0313	0.79
3/64 in	0.0469	1.19
1/16 in	0.0625	1.59
5/64 in	0.0781	1.98
3/32 in	0.0938	2.38
7/64 in	0.1094	2.78
1/8 in	0.1250	3.17
9/64 in	0.1406	3.57
5/32 in	0.1563	3.97
11/64 in	0.1719	4.37
3/16 in	0.1875	4.76
13/64 in	0.2031	5.16
7/32 in	0.2188	5.56
15/64 in	0.2344	5.95
1/4 in	0.2500	6.35
17/64 in	0.2656	6.75
9/32 in	0.2813	7.14
19/64 in	0.2969	7.54
5/16 in	0.3125	7.94
21/64 in	0.3281	8.33
11/32 in	0.3438	8.73
23/64 in	0.3594	9.13
3/8 in	0.3750	9.52
25/64 in	0.3906	9.92
13/32 in	0.4063	10.32
27/64 in	0.4219	10.72
7/16 in	0.4375	11.11
29/64 in	0.4531	11.51
15/32 in	0.4688	11.91
31/64 in	0.4844	12.30
1/2 in	0.5000	12.70
33/64 in	0.5156	13.10
17/32 in	0.5313	13.49
35/64 in	0.5469	13.89
9/16 in	0.5625	14.29
37/64 in	0.5781	14.68
19/32 in	0.5938	15.08
39/64 in	0.6094	15.48
5/8 in	0.6250	15.88
41/64 in	0.6406	16.27
21/32 in	0.6563	16.67
43/64 in	0.6719	17.07
11/16 in	0.6875	17.46
45/64 in	0.7031	17.86
23/32 in	0.7188	18.26
47/64 in	0.7344	18.65
3/4 in	0.7500	19.05
49/64 in	0.7656	19.45
25/32 in	0.7813	19.84
51/64 in	0.7969	20.24
13/16 in	0.8125	20.64
53/64 in	0.8281	21.03
27/32 in	0.8438	21.43
55/64 in	0.8594	21.83
7/8 in	0.8750	22.22
57/64 in	0.8906	22.62
29/32 in	0.9063	23.02
59/64 in	0.9219	23.42
15/16 in	0.9375	23.81
61/64 in	0.9531	24.21
31/32 in	0.9688	24.61
63/64 in	0.9844	25.00
1 in	1.0000	25.40

Number drills, #80 to #1

Drill	Inches	Millimetres
#80	0.0135	0.34
#79	0.0145	0.37
#78	0.0160	0.41
#77	0.0180	0.46
#76	0.0200	0.51
#75	0.0210	0.53
#74	0.0225	0.57
#73	0.0240	0.61
#72	0.0250	0.64
#71	0.0260	0.66
#70	0.0280	0.71
#69	0.0292	0.74
#68	0.0310	0.79
#67	0.0320	0.81
#66	0.0330	0.84
#65	0.0350	0.89
#64	0.0360	0.91
#63	0.0370	0.94
#62	0.0380	0.97
#61	0.0390	0.99
#60	0.0400	1.02
#59	0.0410	1.04
#58	0.0420	1.07
#57	0.0430	1.09
#56	0.0465	1.18
#55	0.0520	1.32
#54	0.0550	1.40
#53	0.0595	1.51
#52	0.0635	1.61
#51	0.0670	1.70
#50	0.0700	1.78
#49	0.0730	1.85
#48	0.0760	1.93
#47	0.0785	1.99
#46	0.0810	2.06
#45	0.0820	2.08
#44	0.0860	2.18
#43	0.0890	2.26
#42	0.0935	2.37
#41	0.0960	2.44
#40	0.0980	2.49
#39	0.0995	2.53
#38	0.1015	2.58
#37	0.1040	2.64
#36	0.1065	2.71
#35	0.1100	2.79
#34	0.1110	2.82
#33	0.1130	2.87
#32	0.1160	2.95
#31	0.1200	3.05
#30	0.1285	3.26
#29	0.1360	3.45
#28	0.1405	3.57
#27	0.1440	3.66
#26	0.1470	3.73
#25	0.1495	3.80
#24	0.1520	3.86
#23	0.1540	3.91
#22	0.1570	3.99
#21	0.1590	4.04
#20	0.1610	4.09
#19	0.1660	4.22
#18	0.1695	4.31
#17	0.1730	4.39
#16	0.1770	4.50
#15	0.1800	4.57
#14	0.1820	4.62
#13	0.1850	4.70
#12	0.1890	4.80
#11	0.1910	4.85
#10	0.1935	4.91
#9	0.1960	4.98
#8	0.1990	5.05
#7	0.2010	5.11
#6	0.2040	5.18
#5	0.2055	5.22
#4	0.2090	5.31
#3	0.2130	5.41
#2	0.2210	5.61
#1	0.2280	5.79

Letter drills, A to Z

Drill	Inches	Millimetres
letter A	0.2340	5.94
letter B	0.2380	6.05
letter C	0.2420	6.15
letter D	0.2460	6.25
letter E	0.2500	6.35
letter F	0.2570	6.53
letter G	0.2610	6.63
letter H	0.2660	6.76
letter I	0.2720	6.91
letter J	0.2770	7.04
letter K	0.2810	7.14
letter L	0.2900	7.37
letter M	0.2950	7.49
letter N	0.3020	7.67
letter O	0.3160	8.03
letter P	0.3230	8.20
letter Q	0.3320	8.43
letter R	0.3390	8.61
letter S	0.3480	8.84
letter T	0.3580	9.09
letter U	0.3680	9.35
letter V	0.3770	9.58
letter W	0.3860	9.80
letter X	0.3970	10.08
letter Y	0.4040	10.26
letter Z	0.4130	10.49

Closest inch drill for each metric size

Metric drills come in 0.1 mm steps. For a quick swap, here is the closest fractional, number or letter drill for each half millimetre.

Metric drill	Closest inch drill	Its size
1.0 mm	#61	0.99 mm
1.5 mm	#53	1.51 mm
2.0 mm	#47	1.99 mm
2.5 mm	#40	2.49 mm
3.0 mm	#31	3.05 mm
3.5 mm	#29	3.45 mm
4.0 mm	#22	3.99 mm
4.5 mm	#16	4.50 mm
5.0 mm	#9	4.98 mm
5.5 mm	7/32 in	5.56 mm
6.0 mm	letter B	6.05 mm
6.5 mm	letter F	6.53 mm
7.0 mm	letter J	7.04 mm
7.5 mm	letter M	7.49 mm
8.0 mm	letter O	8.03 mm
8.5 mm	letter Q	8.43 mm
9.0 mm	letter T	9.09 mm
9.5 mm	3/8 in	9.52 mm
10.0 mm	25/64 in	9.92 mm
10.5 mm	letter Z	10.49 mm
11.0 mm	7/16 in	11.11 mm
11.5 mm	29/64 in	11.51 mm
12.0 mm	15/32 in	11.91 mm
12.5 mm	31/64 in	12.30 mm
13.0 mm	33/64 in	13.10 mm

A close match is not an exact one. Check the diameter before you swap a drill for a tap, because a small difference changes how much thread is left. The calculator shows the effect.

FAQ

What size is a #7 drill?

A #7 drill is 0.2010 in, which is 5.11 mm. It is the standard tap drill for 1/4-20.

Which inch drill is closest to 6 mm?

letter B is the closest, at 0.2380 in (6.05 mm). It is 0.05 mm from 6 mm.

What is the difference between fractional, number and letter drills?

Fractional drills step by 1/64 in, from 1/64 in to 1 in. Number drills run from #80 (0.0135 in) to #1 (0.2280 in), and a bigger number is a smaller drill. Letter drills run from A (0.2340 in) to Z (0.4130 in).

Diameters from Wikipedia: drill bit sizes. Last reviewed October 7, 2026.