What is Thread Pitch & Thread Count?
Thread count is used for deciphering the threads per inch (TPI) for imperial threaded fasteners, and the thread pitch is the dimension between threads for metric fasteners. The thread count or pitch for a fastener is most commonly referenced after the diameter. For example, a 3/8-16 diameter bolt would have 16 threads per inch and a metric M10-1.50 would have 1.50mm between each thread.
| Threads Per Inch (TPI) - Imperial | ||
| Bolt Size | Coarse Thread UNC | Fine Thread UNC |
| #1 | 64 | 72 |
| #2 | 56 | 64 |
| #3 | 48 | 56 |
| #4 | 40 | 48 |
| #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 |
| Thread Pitch - Metric | |||
| Bolt Diameter - mm | Standard | Fine | Extra Fine |
| 2 | .4 | - | - |
| 2.5 | .45 | - | - |
| 3 | .5 | - | - |
| 4 | .7 | - | - |
| 5 | .8 | - | - |
| 6 | 1.0 | - | - |
| 7 | 1.0 | - | - |
| 8 | 1.25 | 1 | - |
| 10 | 1.50 | 1.25 | 1 |
| 12 | 1.75 | 1.50 | 1.25 |
| 14 | 2 | 1.50 | - |
| 16 | 2 | - | - |
| 18 | 2.5 | - | - |
| 20 | 2.5 | - | - |