Engineering quick reference

Drill Size Chart

Number, letter, fractional, and metric drills cross-referenced by decimal-inch equivalent.

Key — Dec. in: decimal-inch equivalent (the compare column) · mm = dec × 25.4 · # series: bigger number = smaller drill · letters grow A → Z

Number — #80 → #147 sizes
Size	Dec. in	mm
#80	0.0135	0.34
#75	0.0210	0.53
#70	0.0280	0.71
#65	0.0350	0.89
#60	0.0400	1.02
#55	0.0520	1.32
#52	0.0635	1.61
#50	0.0700	1.78
#48	0.0760	1.93
#46	0.0810	2.06
#44	0.0860	2.18
#42	0.0935	2.37
#40	0.0980	2.49
#38	0.1015	2.58
#36	0.1065	2.71
#34	0.1110	2.82
#32	0.1160	2.95
#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 — A → Z26 sizes
Size	Dec. in	mm
A	0.2340	5.94
B	0.2380	6.05
C	0.2420	6.15
D	0.2460	6.25
E	0.2500	6.35
F	0.2570	6.53
G	0.2610	6.63
H	0.2660	6.76
I	0.2720	6.91
J	0.2770	7.04
K	0.2810	7.14
L	0.2900	7.37
M	0.2950	7.49
N	0.3020	7.67
O	0.3160	8.03
P	0.3230	8.20
Q	0.3320	8.43
R	0.3390	8.61
S	0.3480	8.84
T	0.3580	9.09
U	0.3680	9.35
V	0.3770	9.58
W	0.3860	9.80
X	0.3970	10.08
Y	0.4040	10.26
Z	0.4130	10.49

Fractional — 1/64 → 1″40 sizes
Size	Dec. in	mm
1/64	0.0156	0.40
1/32	0.0313	0.80
3/64	0.0469	1.19
1/16	0.0625	1.59
5/64	0.0781	1.98
3/32	0.0938	2.38
7/64	0.1094	2.78
1/8	0.1250	3.17
9/64	0.1406	3.57
5/32	0.1563	3.97
11/64	0.1719	4.37
3/16	0.1875	4.76
13/64	0.2031	5.16
7/32	0.2188	5.56
15/64	0.2344	5.95
1/4	0.2500	6.35
17/64	0.2656	6.75
9/32	0.2813	7.15
19/64	0.2969	7.54
5/16	0.3125	7.94
21/64	0.3281	8.33
11/32	0.3438	8.73
23/64	0.3594	9.13
3/8	0.3750	9.52
25/64	0.3906	9.92
13/32	0.4063	10.32
27/64	0.4219	10.72
7/16	0.4375	11.11
29/64	0.4531	11.51
15/32	0.4688	11.91
31/64	0.4844	12.30
1/2	0.5000	12.70
9/16	0.5625	14.29
5/8	0.6250	15.88
11/16	0.6875	17.46
3/4	0.7500	19.05
13/16	0.8125	20.64
7/8	0.8750	22.22
15/16	0.9375	23.81
1"	1.0000	25.40

Metric — 0.5 → 25 mm24 sizes
Size	Dec. in	mm
0.5 mm	0.0197	0.50
1.0 mm	0.0394	1.00
1.5 mm	0.0591	1.50
2.0 mm	0.0787	2.00
2.5 mm	0.0984	2.50
3.0 mm	0.1181	3.00
3.5 mm	0.1378	3.50
4.0 mm	0.1575	4.00
4.5 mm	0.1772	4.50
5.0 mm	0.1969	5.00
5.5 mm	0.2165	5.50
6.0 mm	0.2362	6.00
6.5 mm	0.2559	6.50
7.0 mm	0.2756	7.00
8.0 mm	0.3150	8.00
9.0 mm	0.3543	9.00
10.0 mm	0.3937	10.00
11.0 mm	0.4331	11.00
12.0 mm	0.4724	12.00
14.0 mm	0.5512	14.00
16.0 mm	0.6299	16.00
18.0 mm	0.7087	18.00
20.0 mm	0.7874	20.00
25.0 mm	0.9843	25.00

137 standard sizes, each listed in size order within its series. Decimal equivalents in inches; millimeters = decimal × 25.4. For a searchable cross-reference, an interactive caliper, and thread tap/clearance fits, see the fulldrill size chart.

Free engineering reference from Digital Machine
digitalmachine.com · 805-697-7829 · Located in California

Nominal drill diameters — verify against current ANSI/ASME B94.11M and tool-supplier data for design-critical work. · September 2026