Bolt Size and Threads
Use the table below to determine the diameters and thread counts for common size US-Customary bolts along with the recommended tap drill sizes for a specific thread type/count.

Keep in mind that the clearance hole diameter is a "close fit" type. Typical manufactuing clearance holes are usually 1/32" larger than the bolt diameter.

Gauge/Size Major Dia. (in.) Clearance Drill Typ. Nut Size NC/UNC TPI UNC Tap Drill NF/UNF TPI UNF Tap Drill NS TPI NS Tap Drill
0000
0.020
73
-
160
-
-
-
-
000
0.035
63
3/32"
120
-
-
-
-
00
0.050
55
3/32"
90
-
-
-
-
0
0.060
52
5/32"
-
-
80
-
-
1
0.073
48
5/32"
64
72
56
2
0.086
43
3/16"
56
64
-
-
3
0.099
38
3/16"
48
56
-
-
4
0.112
33
1/4"
40
48
32
-
-
-
-
356
5
0.125
30
1/4"
40
44
36
6
0.138
28
5/16"
32
40
36
7
0.151
23
5/16"
-
-
-
-
30
-
-
-
-
32
-
-
-
-
36
8
0.164
19
11/32"
32
36
30
-
-
-
-
40
9
0.177
15
11/32"
-
-
-
-
24
-
-
-
-
30
-
-
-
-
32
10
0.190
11
3/8"
24
32
28
-
-
-
-
30
12
0.216
2
7/16"
24
-
28
-
32
14
0.242
D
7/16"
-
-
-
-
20
-
-
-
-
24
1/4"
0.250
E
7/16"
20
28
24
-
-
-
-
27
-
-
-
-
32
16
0.268
I
1/2"
-
-
-
-
18
-
-
-
-
20
-
-
-
-
22
18
0.294
19/64"
9/16"
-
-
-
-
18
-
-
-
-
20
5/16"
0.3125
O
9/16"
18
24
20
-
-
-
-
27
-
-
-
-
32
20
0.320
P
5/8"
-
-
-
-
16
-
-
-
-
18
-
-
-
-
20
22
0.346
S
5/8"
-
-
-
-
16
-
-
-
-
18
24
0.372
V
5/8"
-
-
-
-
16
-
-
-
-
18
3/8"
0.375
V
5/8"
16
24
20
-
-
-
-
-
27
-
26
0.398
Y
11/16"
-
-
-
-
14
-
-
-
-
16
28
0.424
7/16"
11/16"
-
-
-
-
14
-
-
-
-
16
23/64"
7/16"
0.4375
7/16"
11/16"
14
20
24
-
-
-
-
-
27
-
30
0.450
29/64"
7/8"
-
-
-
-
14
-
-
-
-
16
1/2"
0.500
1/2"
3/4"
13
20
29/64"
12
-
-
-
-
-
24
-
-
-
-
-
27
-
12
-
-
-
-
-
9/16"
0.5625
9/16"
-
12
18
33/64"
27
-
5/8"
0.6250
5/8"
-
11
17/32"
18
37/64"
12
-
-
-
-
-
27
-
11/16"
0.68753
11/16"
-
-
-
-
-
-
-
3/4"
0.750
3/4"
1-1/8"
10
21/32"
16
-
12
-
-
-
-
-
27
-
7/8"
0.8750
7/8"
1-5/16"
9
49/64"
14
-
12
-
-
-
-
-
18
-
-
-
-
-
27
-
1"
1.0000
1"
1-1/2"
8
7/8"
14
-
12
-
-
-
-
-
27
-