JST - Is it metric or not?

I’m looking for some basic headers for some two pin moment switches.
The idea is to just buy a heap of 2 pin sockets that I can solder directly to a board and use some easy to source plug tails to connect my switches.

I thought JST made a heap of those little white ones. And I see the JST-XH series…

Like these: https://m.media-amazon.com/images/I/51DJV9ba6TL.jpg

But I’m having trouble determining the pitch.
Some sites (core included) lists them as 2.54. Others have them at 2.5.

Which is it?

JST-XH connectors are typically listed with a pitch of 2.54mm. This pitch is often referred to as “standard” or “grid” pitch and is common in many types of electronic components, as it corresponds to 1/10 of an inch. This is also the pitch used in breadboards and perfboards, making these components easy to work with in prototyping.

The confusion between 2.54mm and 2.5mm likely arises from rounding, as 2.54mm converted to inches is exactly 0.1", but when converting back to millimeters, some may round to 2.5mm for simplicity. However, in practical use and in technical specifications, 2.54mm is the correct pitch for these connectors.

I could be wrong though

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Hey Dan,

I think @Cheese71011 is correct with this, the Pitch standard is 2.54mm but often people like to round numbers for whatever reason. JST-XH is a 2.54mm pitch connector, though in future if there is any confusion with the connector types you are looking for, we have a handy little guide for connectors that can be used for reference.


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That was my original thought, but two things throw that out the window.

  1. Check on Mouser or DigiKey and they list the pitch as 0.098" (2.5mm).
  2. JST specs list XH as 2.5mm

So I think it’s 2.5mm but everyone is selling 2.54mm knockoffs calling them JST-XH

Seems strange that DigiKey would round to 2.5mm and then convert to 0.098"…
Especially since JST themselves list 2.5mm

2.54 would be a more logical choice… And that’s actually what I want… But it is weird!

Here’s the PDF from JST…

Hey Dan,

Seems a bit odd, the standard pin pitch for most electronic connectors, perfboards and breadboards are 2.54mm specifically. Regardless, anything under an 8 pin connector shouldn’t really cause too much concern for fitment as there is enough play in most perfboards for that difference.


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That link to the connectors page you sent sheds some more light on the subject! Thanks!!

Note here the * in reference to the XH-JST Connectors, some manufacturers will use 2.54 and 2.5mm pitch interchangeably with connectors with less than 4 pins. Know however the JST standard is to always use the metric system.

So there you go… Officially metric (2.5mm) but some mfgrs just fudge it for <4 pins!


Hi All
I think if you look into this far enough both are listed as “standard” and both are used. And it does not end there. Goes all the way down to 1mm or less. But although you can use whatever you like as a “standard” all the PCB design programs I have come across still use a 2.54 (0.1") or multiples/submultiples of for a grid pattern for their layout so for pin headers etc I would stick with 2.54. Easier all round.
Cheers Bob
As for

This would not get past any decent QA.