I've ran into several posts where the author used 2 systems in the same post. Personally, I use the metric/international system all the time. Other people might use other systems, namely the US system. I'm not really comfortable using it myself but I'm fine if others prefer to use it.

The problem arise when the two are mixed in alternation, it's annoying. I think the users can use any system as long as they use it consistently.

What do others think about this?

  • $\begingroup$ I typically do my measurements in the US system, but I try to include conversions regardless. Are you taking issue with this, or just inconsistency in picking which set to use? $\endgroup$
    – Frostfyre
    Commented Aug 4, 2015 at 16:30
  • 3
    $\begingroup$ If the two systems are being used to describe the same type of measurement, that is strange, but if they're different types (like using meters and Farenheit), that might just be how the answerer learned it $\endgroup$ Commented Aug 4, 2015 at 17:03
  • $\begingroup$ That happened to me here (not the mixing, but the use of the 'merican system). Someone pointed it out and I added the metric system. $\endgroup$
    – Samuel
    Commented Aug 4, 2015 at 21:56
  • $\begingroup$ I think I've done the mixing before, when I am combining several sources into one answer - one source has metric and other US and I (eventually) convert one of them into the other to do a calculation, but I might have had steps to do before I was able to convert. $\endgroup$ Commented Aug 6, 2015 at 23:00

2 Answers 2


I agree that this kind of thing is really annoying (though I've probably been guilty of it myself in the past). SI units are the most common ones in science, and given that most of the familiar constants are best known as their SI unit values (e.g. the value of $c$ is ~ 300,000,000 meters/second), I think that they are our best choice.

Either way, consistency in a given post is important. We don't need to have consistency across the board, though - for example, if I reference a table of statistics about population density, I might be working in acres. That could be okay to use across the post, but if there aren't too many numbers, then conversions should be used. Let's not be lazy.

  • 1
    $\begingroup$ Relevant XKCD: Degrees $\endgroup$
    – user
    Commented Feb 15, 2016 at 13:47

I agree, that one unit of measure should generally be used in a post. I fear I might be one of your culprits though.


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