Drill bit to screw size

Pick a screw and a purpose to get the drill, then the nearest common bit in each series.

Screw

Purpose

Thread, fit or material

Match my screw

Example: for #8-32 the tap drill is #29 (0.1360 in) and the close-fit clearance hole is #18.

Drill bit charts

Number drills (#1 to #80)

Drill	Inch	mm
#1	0.228	5.791
#2	0.221	5.613
#3	0.213	5.41
#4	0.209	5.309
#5	0.2055	5.22
#6	0.204	5.182
#7	0.201	5.105
#8	0.199	5.055
#9	0.196	4.978
#10	0.1935	4.915
#11	0.191	4.851
#12	0.189	4.801
#13	0.185	4.699
#14	0.182	4.623
#15	0.18	4.572
#16	0.177	4.496
#17	0.173	4.394
#18	0.1695	4.305
#19	0.166	4.216
#20	0.161	4.089
#21	0.159	4.039
#22	0.157	3.988
#23	0.154	3.912
#24	0.152	3.861
#25	0.1495	3.797
#26	0.147	3.734
#27	0.144	3.658
#28	0.1405	3.569
#29	0.136	3.454
#30	0.1285	3.264
#31	0.12	3.048
#32	0.116	2.946
#33	0.113	2.87
#34	0.111	2.819
#35	0.11	2.794
#36	0.1065	2.705
#37	0.104	2.642
#38	0.1015	2.578
#39	0.0995	2.527
#40	0.098	2.489
#41	0.096	2.438
#42	0.0935	2.375
#43	0.089	2.261
#44	0.086	2.184
#45	0.082	2.083
#46	0.081	2.057
#47	0.0785	1.994
#48	0.076	1.93
#49	0.073	1.854
#50	0.07	1.778
#51	0.067	1.702
#52	0.0635	1.613
#53	0.0595	1.511
#54	0.055	1.397
#55	0.052	1.321
#56	0.0465	1.181
#57	0.043	1.092
#58	0.042	1.067
#59	0.041	1.041
#60	0.04	1.016
#61	0.039	0.991
#62	0.038	0.965
#63	0.037	0.94
#64	0.036	0.914
#65	0.035	0.889
#66	0.033	0.838
#67	0.032	0.813
#68	0.031	0.787
#69	0.0292	0.742
#70	0.028	0.711
#71	0.026	0.66
#72	0.025	0.635
#73	0.024	0.61
#74	0.0225	0.571
#75	0.021	0.533
#76	0.02	0.508
#77	0.018	0.457
#78	0.016	0.406
#79	0.0145	0.368
#80	0.0135	0.343

Letter drills (A to Z)

Drill	Inch	mm
A	0.234	5.944
B	0.238	6.045
C	0.242	6.147
D	0.246	6.248
E	0.25	6.35
F	0.257	6.528
G	0.261	6.629
H	0.266	6.756
I	0.272	6.909
J	0.277	7.036
K	0.281	7.137
L	0.29	7.366
M	0.295	7.493
N	0.302	7.671
O	0.316	8.026
P	0.323	8.204
Q	0.332	8.433
R	0.339	8.611
S	0.348	8.839
T	0.358	9.093
U	0.368	9.347
V	0.377	9.576
W	0.386	9.804
X	0.397	10.084
Y	0.404	10.262
Z	0.413	10.49

Fractional drills (1/64 to 1-1/4 in)

Drill	Inch	mm
1/64	0.0156	0.397
1/32	0.0313	0.794
3/64	0.0469	1.191
1/16	0.0625	1.588
5/64	0.0781	1.984
3/32	0.0938	2.381
7/64	0.1094	2.778
1/8	0.125	3.175
9/64	0.1406	3.572
5/32	0.1563	3.969
11/64	0.1719	4.366
3/16	0.1875	4.762
13/64	0.2031	5.159
7/32	0.2188	5.556
15/64	0.2344	5.953
1/4	0.25	6.35
17/64	0.2656	6.747
9/32	0.2813	7.144
19/64	0.2969	7.541
5/16	0.3125	7.938
21/64	0.3281	8.334
11/32	0.3438	8.731
23/64	0.3594	9.128
3/8	0.375	9.525
25/64	0.3906	9.922
13/32	0.4063	10.319
27/64	0.4219	10.716
7/16	0.4375	11.112
29/64	0.4531	11.509
15/32	0.4688	11.906
31/64	0.4844	12.303
1/2	0.5	12.7
33/64	0.5156	13.097
17/32	0.5313	13.494
35/64	0.5469	13.891
9/16	0.5625	14.288
37/64	0.5781	14.684
19/32	0.5938	15.081
39/64	0.6094	15.478
5/8	0.625	15.875
41/64	0.6406	16.272
21/32	0.6563	16.669
43/64	0.6719	17.066
11/16	0.6875	17.463
45/64	0.7031	17.859
23/32	0.7188	18.256
47/64	0.7344	18.653
3/4	0.75	19.05
49/64	0.7656	19.447
25/32	0.7813	19.844
51/64	0.7969	20.241
13/16	0.8125	20.638
53/64	0.8281	21.034
27/32	0.8438	21.431
55/64	0.8594	21.828
7/8	0.875	22.225
57/64	0.8906	22.622
29/32	0.9063	23.019
59/64	0.9219	23.416
15/16	0.9375	23.813
61/64	0.9531	24.209
31/32	0.9688	24.606
63/64	0.9844	25.003
1	1.0	25.4
1-1/64	1.0156	25.797
1-1/32	1.0313	26.194
1-3/64	1.0469	26.591
1-1/16	1.0625	26.987
1-5/64	1.0781	27.384
1-3/32	1.0938	27.781
1-7/64	1.1094	28.178
1-1/8	1.125	28.575
1-9/64	1.1406	28.972
1-5/32	1.1563	29.369
1-11/64	1.1719	29.766
1-3/16	1.1875	30.162
1-13/64	1.2031	30.559
1-7/32	1.2188	30.956
1-15/64	1.2344	31.353
1-1/4	1.25	31.75

Metric drills

Drill	Inch	mm
0.5 mm	0.0197	0.5
0.8 mm	0.0315	0.8
1.0 mm	0.0394	1.0
1.25 mm	0.0492	1.25
1.5 mm	0.0591	1.5
1.6 mm	0.063	1.6
1.7 mm	0.0669	1.7
1.8 mm	0.0709	1.8
2.0 mm	0.0787	2.0
2.05 mm	0.0807	2.05
2.2 mm	0.0866	2.2
2.4 mm	0.0945	2.4
2.5 mm	0.0984	2.5
2.6 mm	0.1024	2.6
2.7 mm	0.1063	2.7
2.9 mm	0.1142	2.9
3.0 mm	0.1181	3.0
3.1 mm	0.122	3.1
3.2 mm	0.126	3.2
3.3 mm	0.1299	3.3
3.4 mm	0.1339	3.4
3.5 mm	0.1378	3.5
3.6 mm	0.1417	3.6
3.7 mm	0.1457	3.7
3.9 mm	0.1535	3.9
4.0 mm	0.1575	4.0
4.2 mm	0.1654	4.2
4.3 mm	0.1693	4.3
4.5 mm	0.1772	4.5
4.8 mm	0.189	4.8
5.0 mm	0.1969	5.0
5.25 mm	0.2067	5.25
5.3 mm	0.2087	5.3
5.5 mm	0.2165	5.5
5.8 mm	0.2283	5.8
6.0 mm	0.2362	6.0
6.4 mm	0.252	6.4
6.5 mm	0.2559	6.5
6.6 mm	0.2598	6.6
6.8 mm	0.2677	6.8
7.0 mm	0.2756	7.0
8.0 mm	0.315	8.0
8.4 mm	0.3307	8.4
8.5 mm	0.3346	8.5
8.75 mm	0.3445	8.75
9.0 mm	0.3543	9.0
10.0 mm	0.3937	10.0
10.2 mm	0.4016	10.2
10.5 mm	0.4134	10.5
10.75 mm	0.4232	10.75
11.0 mm	0.4331	11.0
12.0 mm	0.4724	12.0
12.5 mm	0.4921	12.5
13.0 mm	0.5118	13.0
13.5 mm	0.5315	13.5
14.0 mm	0.5512	14.0
14.5 mm	0.5709	14.5
15.0 mm	0.5906	15.0
15.5 mm	0.6102	15.5
16.0 mm	0.6299	16.0
16.5 mm	0.6496	16.5
17.0 mm	0.6693	17.0
17.5 mm	0.689	17.5
18.0 mm	0.7087	18.0
18.5 mm	0.7283	18.5
19.0 mm	0.748	19.0
19.5 mm	0.7677	19.5
20.0 mm	0.7874	20.0
20.5 mm	0.8071	20.5
21.0 mm	0.8268	21.0
22.0 mm	0.8661	22.0
23.0 mm	0.9055	23.0
24.0 mm	0.9449	24.0
25.0 mm	0.9843	25.0
26.0 mm	1.0236	26.0
28.0 mm	1.1024	28.0

How the four drill series work

Drill bits are sold in four overlapping sets. Number drills run from #1 (0.228 in) down to #80. Letter drills run from A (0.234 in) up to Z. Fractional drills step in sixty-fourths of an inch from 1/64 in. Metric drills are sized in millimetres. The finder shows the nearest bit in each, with the difference from the ideal size, so you can use whichever set you own.

Choosing the purpose

Pick tap drill when you will cut a thread with a tap. Pick clearance when the screw should pass through freely. Pick pilot for wood screws. If the nearest bit is larger than the ideal size, expect a looser fit; if it is smaller, expect to work harder to drive or tap. When in doubt, test on scrap material.