Convert Threads per inch to Thread pitch — Machining & CNC
Formula
pitch(mm) = 25.4 ÷ TPI
Why this matters in machining & cnc
Imperial threads are specified in threads per inch; metric threads by pitch (mm). 20 TPI = 1.27 mm pitch. Inverse relationship — higher TPI means finer (smaller) pitch.
Threads per inch to Thread pitch reference table
| Threads per inch (TPI) | Thread pitch (mm) |
|---|---|
| 8 | 3.175 |
| 10 | 2.54 |
| 13 | 1.9538 |
| 16 | 1.5875 |
| 18 | 1.4111 |
| 20 | 1.27 |
| 24 | 1.0583 |
| 28 | 0.9071 |
| 32 | 0.7938 |