Thread Pitch Converter
Convert screw thread pitch between millimetres and threads per inch (TPI) — for matching bolts, nuts and taps in the workshop. Enter a value in either unit and get the exact conversion instantly.
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How to use
- Enter the thread pitch in millimetres, for example 1.25.
- The matching value in threads per inch (TPI) appears at once.
- Enter a TPI value instead to convert back to millimetres.
- Check a reading by hand with TPI = 25.4 ÷ pitch in mm.
Good to know
- Common coarse pitches: M6×1.0, M8×1.25, M10×1.5, M12×1.75 — useful for quick identification.
- TPI = 25.4 ÷ pitch(mm), so a 1.25 mm pitch equals about 20.3 TPI.
- Bolt identity needs both diameter and pitch — pitch alone is not enough.
Note
TPI = 25.4 / pitch (mm). Common metric coarse pitches: M6 = 1.0 mm, M8 = 1.25 mm, M10 = 1.5 mm, M12 = 1.75 mm. Bolt size is made from diameter and pitch together.
Frequently Asked Questions (FAQ)
How do I convert mm pitch to TPI?
Enter the metric pitch in mm. The tool uses TPI equals 25.4 divided by pitch in mm and updates live.
Can I convert TPI to mm?
Yes. Enter a TPI value and the tool converts it back to mm pitch instantly.
What are common metric coarse pitches?
M6 is 1.0 mm, M8 is 1.25 mm, M10 is 1.5 mm and M12 is 1.75 mm.
Is it free?
Yes. It is free, needs no signup and runs in your browser.