US Threads Per Inch Table
Bolt Size |
Threads Per Inch (TPI) |
Coarse Thread
UNC |
Fine Thread
UNF |
#0000 |
- |
160 |
#000 |
- |
120 |
#00 |
- |
90 |
#0 |
- |
80 |
#1 |
64 |
72 |
#2 |
56 |
64 |
#3 |
48 |
56 |
#4 |
40 |
48 |
#5 |
40 |
44 |
#6 |
32 |
40 |
#8 |
32 |
36 |
#10 |
24 |
32 |
#12 |
24 |
28 |
1/4" |
20 |
28 |
5/16" |
18 |
24 |
3/8" |
16 |
24 |
7/16" |
14 |
20 |
1/2" |
13 |
20 |
9/16" |
12 |
18 |
5/8" |
11 |
18 |
3/4" |
10 |
16 |
7/8" |
9 |
14 |
1" |
8 |
12* |
1-1/8" |
7 |
12 |
1-1/4" |
7 |
12 |
1-1/2" |
6 |
12 |
* 12tpi is the UNF standard however 14tpi
is far more common in actual use. |