Drill bit size chart

Every standard twist drill size from the smallest number drill to 1 inch and 25 mm, smallest first, with its size in decimal inches and millimetres. Four series overlap: number drills (#80, the smallest, to #1), letter drills (A to Z), fractional drills in 1/64 inch steps, and metric drills.

From the standard, ASME B94.11M, checked against three copies

Reading the chart

Number and letter drills fill the gaps between the fractional sizes, which is why a pilot-hole chart sometimes names a drill like #29 or F. Some sizes have two names: letter E is exactly 1/4 inch.

Which drill for a screw is on the pilot hole chart.

Drill	Series	Inches	mm
0.3 mm	Metric	0.0118	0.3
#80	Number	0.0135	0.34
#79	Number	0.0145	0.37
1/64	Fraction	0.0156	0.4
0.4 mm	Metric	0.0157	0.4
#78	Number	0.016	0.41
#77	Number	0.018	0.46
0.5 mm	Metric	0.0197	0.5
#76	Number	0.02	0.51
#75	Number	0.021	0.53
#74	Number	0.0225	0.57
0.6 mm	Metric	0.0236	0.6
#73	Number	0.024	0.61
#72	Number	0.025	0.64
#71	Number	0.026	0.66
0.7 mm	Metric	0.0276	0.7
#70	Number	0.028	0.71
#69	Number	0.0292	0.74
#68	Number	0.031	0.79
1/32	Fraction	0.0313	0.79
0.8 mm	Metric	0.0315	0.8
#67	Number	0.032	0.81
#66	Number	0.033	0.84
#65	Number	0.035	0.89
0.9 mm	Metric	0.0354	0.9
#64	Number	0.036	0.91
#63	Number	0.037	0.94
#62	Number	0.038	0.97
#61	Number	0.039	0.99
1 mm	Metric	0.0394	1
#60	Number	0.04	1.02
#59	Number	0.041	1.04
#58	Number	0.042	1.07
#57	Number	0.043	1.09
1.1 mm	Metric	0.0433	1.1
#56	Number	0.0465	1.18
3/64	Fraction	0.0469	1.19
1.2 mm	Metric	0.0472	1.2
1.3 mm	Metric	0.0512	1.3
#55	Number	0.052	1.32
#54	Number	0.055	1.4
1.4 mm	Metric	0.0551	1.4
1.5 mm	Metric	0.0591	1.5
#53	Number	0.0595	1.51
1/16	Fraction	0.0625	1.59
1.6 mm	Metric	0.063	1.6
#52	Number	0.0635	1.61
1.7 mm	Metric	0.0669	1.7
#51	Number	0.067	1.7
#50	Number	0.07	1.78
1.8 mm	Metric	0.0709	1.8
#49	Number	0.073	1.85
1.9 mm	Metric	0.0748	1.9
#48	Number	0.076	1.93
5/64	Fraction	0.0781	1.98
#47	Number	0.0785	1.99
2 mm	Metric	0.0787	2
#46	Number	0.081	2.06
#45	Number	0.082	2.08
2.1 mm	Metric	0.0827	2.1
#44	Number	0.086	2.18
2.2 mm	Metric	0.0866	2.2
#43	Number	0.089	2.26
2.3 mm	Metric	0.0906	2.3
#42	Number	0.0935	2.37
3/32	Fraction	0.0938	2.38
2.4 mm	Metric	0.0945	2.4
#41	Number	0.096	2.44
#40	Number	0.098	2.49
2.5 mm	Metric	0.0984	2.5
#39	Number	0.0995	2.53
#38	Number	0.1015	2.58
2.6 mm	Metric	0.1024	2.6
#37	Number	0.104	2.64
2.7 mm	Metric	0.1063	2.7
#36	Number	0.1065	2.71
7/64	Fraction	0.1094	2.78
#35	Number	0.11	2.79
2.8 mm	Metric	0.1102	2.8
#34	Number	0.111	2.82
#33	Number	0.113	2.87
2.9 mm	Metric	0.1142	2.9
#32	Number	0.116	2.95
3 mm	Metric	0.1181	3
#31	Number	0.12	3.05
3.1 mm	Metric	0.122	3.1
1/8	Fraction	0.125	3.18
3.2 mm	Metric	0.126	3.2
#30	Number	0.1285	3.26
3.3 mm	Metric	0.1299	3.3
3.4 mm	Metric	0.1339	3.4
#29	Number	0.136	3.45
3.5 mm	Metric	0.1378	3.5
#28	Number	0.1405	3.57
9/64	Fraction	0.1406	3.57
3.6 mm	Metric	0.1417	3.6
#27	Number	0.144	3.66
3.7 mm	Metric	0.1457	3.7
#26	Number	0.147	3.73
#25	Number	0.1495	3.8
3.8 mm	Metric	0.1496	3.8
#24	Number	0.152	3.86
3.9 mm	Metric	0.1535	3.9
#23	Number	0.154	3.91
5/32	Fraction	0.1563	3.97
#22	Number	0.157	3.99
4 mm	Metric	0.1575	4
#21	Number	0.159	4.04
#20	Number	0.161	4.09
4.1 mm	Metric	0.1614	4.1
4.2 mm	Metric	0.1654	4.2
#19	Number	0.166	4.22
4.3 mm	Metric	0.1693	4.3
#18	Number	0.1695	4.31
11/64	Fraction	0.1719	4.37
#17	Number	0.173	4.39
4.4 mm	Metric	0.1732	4.4
#16	Number	0.177	4.5
4.5 mm	Metric	0.1772	4.5
#15	Number	0.18	4.57
4.6 mm	Metric	0.1811	4.6
#14	Number	0.182	4.62
#13	Number	0.185	4.7
4.7 mm	Metric	0.185	4.7
3/16	Fraction	0.1875	4.76
4.8 mm	Metric	0.189	4.8
#12	Number	0.189	4.8
#11	Number	0.191	4.85
4.9 mm	Metric	0.1929	4.9
#10	Number	0.1935	4.91
#9	Number	0.196	4.98
5 mm	Metric	0.1969	5
#8	Number	0.199	5.05
5.1 mm	Metric	0.2008	5.1
#7	Number	0.201	5.11
13/64	Fraction	0.2031	5.16
#6	Number	0.204	5.18
5.2 mm	Metric	0.2047	5.2
#5	Number	0.2055	5.22
5.3 mm	Metric	0.2087	5.3
#4	Number	0.209	5.31
5.4 mm	Metric	0.2126	5.4
#3	Number	0.213	5.41
5.5 mm	Metric	0.2165	5.5
7/32	Fraction	0.2188	5.56
5.6 mm	Metric	0.2205	5.6
#2	Number	0.221	5.61
5.7 mm	Metric	0.2244	5.7
#1	Number	0.228	5.79
5.8 mm	Metric	0.2283	5.8
5.9 mm	Metric	0.2323	5.9
A	Letter	0.234	5.94
15/64	Fraction	0.2344	5.95
6 mm	Metric	0.2362	6
B	Letter	0.238	6.05
6.1 mm	Metric	0.2402	6.1
C	Letter	0.242	6.15
6.2 mm	Metric	0.2441	6.2
D	Letter	0.246	6.25
6.3 mm	Metric	0.248	6.3
E	Letter	0.25	6.35
1/4	Fraction	0.25	6.35
6.4 mm	Metric	0.252	6.4
6.5 mm	Metric	0.2559	6.5
F	Letter	0.257	6.53
6.6 mm	Metric	0.2598	6.6
G	Letter	0.261	6.63
6.7 mm	Metric	0.2638	6.7
17/64	Fraction	0.2656	6.75
H	Letter	0.266	6.76
6.8 mm	Metric	0.2677	6.8
6.9 mm	Metric	0.2717	6.9
I	Letter	0.272	6.91
7 mm	Metric	0.2756	7
J	Letter	0.277	7.04
7.1 mm	Metric	0.2795	7.1
K	Letter	0.281	7.14
9/32	Fraction	0.2813	7.14
7.2 mm	Metric	0.2835	7.2
7.3 mm	Metric	0.2874	7.3
L	Letter	0.29	7.37
7.4 mm	Metric	0.2913	7.4
M	Letter	0.295	7.49
7.5 mm	Metric	0.2953	7.5
19/64	Fraction	0.2969	7.54
7.6 mm	Metric	0.2992	7.6
N	Letter	0.302	7.67
7.7 mm	Metric	0.3031	7.7
7.8 mm	Metric	0.3071	7.8
7.9 mm	Metric	0.311	7.9
5/16	Fraction	0.3125	7.94
8 mm	Metric	0.315	8
O	Letter	0.316	8.03
8.1 mm	Metric	0.3189	8.1
8.2 mm	Metric	0.3228	8.2
P	Letter	0.323	8.2
8.3 mm	Metric	0.3268	8.3
21/64	Fraction	0.3281	8.33
8.4 mm	Metric	0.3307	8.4
Q	Letter	0.332	8.43
8.5 mm	Metric	0.3346	8.5
8.6 mm	Metric	0.3386	8.6
R	Letter	0.339	8.61
8.7 mm	Metric	0.3425	8.7
11/32	Fraction	0.3438	8.73
8.8 mm	Metric	0.3465	8.8
S	Letter	0.348	8.84
8.9 mm	Metric	0.3504	8.9
9 mm	Metric	0.3543	9
T	Letter	0.358	9.09
9.1 mm	Metric	0.3583	9.1
23/64	Fraction	0.3594	9.13
9.2 mm	Metric	0.3622	9.2
9.3 mm	Metric	0.3661	9.3
U	Letter	0.368	9.35
9.4 mm	Metric	0.3701	9.4
9.5 mm	Metric	0.374	9.5
3/8	Fraction	0.375	9.53
V	Letter	0.377	9.58
9.6 mm	Metric	0.378	9.6
9.7 mm	Metric	0.3819	9.7
9.8 mm	Metric	0.3858	9.8
W	Letter	0.386	9.8
9.9 mm	Metric	0.3898	9.9
25/64	Fraction	0.3906	9.92
10 mm	Metric	0.3937	10
X	Letter	0.397	10.08
10.1 mm	Metric	0.3976	10.1
10.2 mm	Metric	0.4016	10.2
Y	Letter	0.404	10.26
10.3 mm	Metric	0.4055	10.3
13/32	Fraction	0.4063	10.32
10.4 mm	Metric	0.4094	10.4
Z	Letter	0.413	10.49
10.5 mm	Metric	0.4134	10.5
10.6 mm	Metric	0.4173	10.6
10.7 mm	Metric	0.4213	10.7
27/64	Fraction	0.4219	10.72
10.8 mm	Metric	0.4252	10.8
10.9 mm	Metric	0.4291	10.9
11 mm	Metric	0.4331	11
11.1 mm	Metric	0.437	11.1
7/16	Fraction	0.4375	11.11
11.2 mm	Metric	0.4409	11.2
11.3 mm	Metric	0.4449	11.3
11.4 mm	Metric	0.4488	11.4
11.5 mm	Metric	0.4528	11.5
29/64	Fraction	0.4531	11.51
11.6 mm	Metric	0.4567	11.6
11.7 mm	Metric	0.4606	11.7
11.8 mm	Metric	0.4646	11.8
11.9 mm	Metric	0.4685	11.9
15/32	Fraction	0.4688	11.91
12 mm	Metric	0.4724	12
12.1 mm	Metric	0.4764	12.1
12.2 mm	Metric	0.4803	12.2
12.3 mm	Metric	0.4843	12.3
31/64	Fraction	0.4844	12.3
12.4 mm	Metric	0.4882	12.4
12.5 mm	Metric	0.4921	12.5
12.6 mm	Metric	0.4961	12.6
12.7 mm	Metric	0.5	12.7
1/2	Fraction	0.5	12.7
12.8 mm	Metric	0.5039	12.8
12.9 mm	Metric	0.5079	12.9
13 mm	Metric	0.5118	13
33/64	Fraction	0.5156	13.1
17/32	Fraction	0.5313	13.49
13.5 mm	Metric	0.5315	13.5
35/64	Fraction	0.5469	13.89
14 mm	Metric	0.5512	14
9/16	Fraction	0.5625	14.29
14.5 mm	Metric	0.5709	14.5
37/64	Fraction	0.5781	14.68
15 mm	Metric	0.5906	15
19/32	Fraction	0.5938	15.08
39/64	Fraction	0.6094	15.48
15.5 mm	Metric	0.6102	15.5
5/8	Fraction	0.625	15.88
16 mm	Metric	0.6299	16
41/64	Fraction	0.6406	16.27
16.5 mm	Metric	0.6496	16.5
21/32	Fraction	0.6563	16.67
17 mm	Metric	0.6693	17
43/64	Fraction	0.6719	17.07
11/16	Fraction	0.6875	17.46
17.5 mm	Metric	0.689	17.5
45/64	Fraction	0.7031	17.86
18 mm	Metric	0.7087	18
23/32	Fraction	0.7188	18.26
18.5 mm	Metric	0.7283	18.5
47/64	Fraction	0.7344	18.65
19 mm	Metric	0.748	19
3/4	Fraction	0.75	19.05
49/64	Fraction	0.7656	19.45
19.5 mm	Metric	0.7677	19.5
25/32	Fraction	0.7813	19.84
20 mm	Metric	0.7874	20
51/64	Fraction	0.7969	20.24
20.5 mm	Metric	0.8071	20.5
13/16	Fraction	0.8125	20.64
21 mm	Metric	0.8268	21
53/64	Fraction	0.8281	21.03
27/32	Fraction	0.8438	21.43
21.5 mm	Metric	0.8465	21.5
55/64	Fraction	0.8594	21.83
22 mm	Metric	0.8661	22
7/8	Fraction	0.875	22.23
22.5 mm	Metric	0.8858	22.5
57/64	Fraction	0.8906	22.62
23 mm	Metric	0.9055	23
29/32	Fraction	0.9063	23.02
59/64	Fraction	0.9219	23.42
23.5 mm	Metric	0.9252	23.5
15/16	Fraction	0.9375	23.81
24 mm	Metric	0.9449	24
61/64	Fraction	0.9531	24.21
24.5 mm	Metric	0.9646	24.5
31/32	Fraction	0.9688	24.61
25 mm	Metric	0.9843	25
63/64	Fraction	0.9844	25
1	Fraction	1	25.4

Sources

ASME, B94.11M, Twist drills: fractional, number, letter and metric sizes (via BreakingChips’ check of three copies)
Wikipedia, Engineers Edge and Newman Tools, Drill size and decimal equivalent charts after ASME B94.11M (all 106 number and letter sizes agree but two single-copy outliers), read 2026-11-04
NIST, Special Publication 811, Appendix B (1 in = 25.4 mm)

How we source these numbers