Thread Pitch & TPI Converter
A free, browser-based converter. Runs entirely in your browser — no sign up, nothing stored.
Enter Values
How to use this calculator
- Enter either the thread pitch in mm (metric) or the threads per inch (imperial).
- Leave the other field blank.
- Read the converted value.
How it works
The Thread Pitch & TPI Converter switches between metric pitch and imperial threads-per-inch.
Pitch is the distance between adjacent threads. Since there are 25.4 mm per inch, pitch(mm) = 25.4 / TPI and TPI = 25.4 / pitch(mm).
Worked example
20 TPI. Pitch = 25.4 ÷ 20 = 1.27 mm per thread.
Frequently asked questions
Is pitch the same as lead?
For a single-start thread, yes. For multi-start threads the lead (advance per turn) is the pitch multiplied by the number of starts.
Does this identify a thread standard?
No — it only converts the pitch. Matching a thread also needs the diameter and form (e.g. metric M, UNC/UNF, BSP).
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.