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. |