US Threads Per Inch Table
US (inch) screws are commonly* classified as either Coarse or Fine thread by the 'Threads Per Inch' (TPI) measured along the fastener. TPI is only used on US screws, as metric use a very different Thread Pitch classification and are not interchangeable.
Below is a table that shows screw sizes and the relevant UNC and UNF versions (if any). Some are very common, others are not (I'm looking at you #5-44).
| Screw Size | Threads Per Inch (TPI.) | |
| Coarse / UNC | Fine / UNF | |
| #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 |
* Note - in addition to UNC (Coarse Thread) and UNF (Fine Thread) there is a much less common UNEF (extra fine) thread that is not listed here as it really is not widely used in practice.