Nomenclature: The "mil"


Looking for what most in these forums understand a “mil” to be. You would think this to be obvious but it is not unless you are from one industry. I have contracted all over the world and generally, in Metric countries, a “mil” spoken refers to one millimeter. In Imperial countries it depends what part you are in and what industry you are in. In US auto build shops in the mid-west a mil is one millimeter. In South and West a mil is one thousandth of an inch. In the NE and especially in print shops that include some pcb work and photographic lithography the spoken “mil” refers to one millionth of an inch. Metric low values for microns are often spoken as “mikes”.

So far, the Fritzing world I have seen a “mil” referenced as, just one example, 2.5mm being 0.254 mils with talk being about a header that is actually 0.1" or 2.54mm; nomenclature is all over the map. I’m getting ready to finalize some things and while I am pretty sure I have what I need for my purposes this is bugging me.

In the Fritzing world, what does “mil” mean to you ?

Thanks !


I’m from a mech eng world, and I had never heard about mil until I started electronics 2 years ago. It’s always been thou for me. I figure it’s just a legacy of the industry, like how the world uses a mash of inch and metric on tyre sizes these days.


I’m with Old_Grey, I assume mil is thousandth (usually of an inch). I will point out however that fritzing itself doesn’t care what we call a mil, it uses what ever units are set in the underlying xml/svg files to render. If whoever made the part you are using was confused and set the size / scale wrong that can be a problem though (but since you have source to the part you can with sufficient experience or help from someone here, fix it).



I use Inkscape for all the parts I have made. I fixed the templates to be scaled correctly. I’ve been making comments in my Fritzing prints that others may see that everything sourced by me does not mix Metric and Imperial terms, and to not use the term “mil” anywhere to avoid confusion.

I like this and think it is worthwhile to contribute to. I can tell a lot of effort has been put into this but don’t see much activity on the dev side for about a year per github. I like this project enough maybe I’ll look into merging some of the pulls. /shrug will see.


Yes, there is an amazing amount of good design in fritzing and developers is our strongest need, because as you note development has stalled. Once I finish a python script to check parts I intend on trying to fix bugs. However at present the head on github doesn’t build correctly and has a problem on a very large commit to the gerber generation code which breaks gerber output. I’m not a developer, so I’m not sure how far I’ll get but we will get no where if we don’t try. The lack of real developers to provide advise is I think going to be a problem though.