How to convert pitch mm to tpi

US threads are expressed in tpi - threads per inch. Metric is Pitch mm. I have a 16mm threaded rod that I am trying to buy the right nut for. It has 13 tpi. What pitch mm is that?

US threads are expressed in tpi - threads per inch. Metric is Pitch mm. I have a 16mm threaded rod that I am trying to buy the right nut for. It has 13 tpi. What pitch mm is that?

There are 25.4 mm/inch. If you have 13 threads per inch,
then your metric pitch is 25.4 mm/in divided by 13 threads per in = 1.95 mm/thread.

You probably have a slight error in your thread measurement, and it is really 2 mm pitch. Do you have a metric ruler? Count off ten threads (easier to measure) and see if 10 threads = 20 mm.

But are you sure it is metric rod? 16 mm is very close to 5/8". You might be looking for 5/8" - 13 nut. Threads are NOT very interchangable. You really need to know if it is metric or UNC thread.