The comments in this post discuss this issue, though without a clear conclusion unless I'm missing something.

For something as simple as grams per mole for example, there are actually several ways of displaying the units:

1) g/mol
2) $\mathrm{g/mol}$
3) $\mathrm{g~mol^{-1}}$
4) $\mathrm{g\dot\ mol^{-1}}$
5) $\mathrm{\frac{g}{mol}}$

And probably more.

I suspect that 3 is the best way in-line and either 3 or 5 when not in-line? I don't know, that's why I'm asking ;)

But to reiterate my main question: should fractional units be displayed as fractions or as negative exponents. And if the answer is "depends", then on what?

  • 1
    $\begingroup$ You should really stop by chat sometime, airhuff. Things like this get batted around a lot. (A lot of the time nothing ever really happens about them, but we talk about them... ;-) $\endgroup$
    – hBy2Py
    Mar 25, 2017 at 3:34
  • 1
    $\begingroup$ @hBy2Py Try typing [chat] in a comment ;) Also, you either lost your mouth, or you forgot to close your parentheses. Tut-tut. $\endgroup$ Mar 25, 2017 at 13:24
  • $\begingroup$ @orthocresol [chat] doesn't go straight to Periodic Table, though. I used to double the parenthesis in this kind of situation, but I ended up deciding that I preferred the syntactic irregularity to the visual unpleasantness of the double-paren. (I'm one of those types that will use square brackets, curly braces, etc. in regular text.) $\endgroup$
    – hBy2Py
    Mar 25, 2017 at 13:55

1 Answer 1


Since we're not a professional publishing house, and since there's no ultimate editorial authority enforcing conformity to style, I suspect the ultimate answers to your questions are indeed:

  1. Depends.
  2. On however any given author feels like formatting them.

Thus, if a post has units formatted in a way that is unambiguous and sufficiently easy to read, those units expressions should just be left alone.

In situations where the units are poorly formatted by whatever measure, though—misspelled, wrong punctuation, ambiguous, etc.—I'd be mildly in favor of establishing a semi-formal site-wide recommendation for how they be formatted. I tend to prefer $\#3$, myself, as it is cleaner than $\#4$ (despite Loong's comment using $\#4$ at the linked post) and usually makes it less ambiguous as to which quantities are in the numerator/denominator. That said, $\#2$ involves a lot less typing, which is worth something. I do think any recommendation should include the use of MathJax since exponents will often be required, which leaves out $\#1$. Per Loong's other comment $\#5$ should apparently be shunned (SHUNNED) in polite technical discourse. (Full disclosure: I've formatted inline units that way more than once. {{{SHAME}}})

Despite all that: as long as an edit re-formats unit expressions in a way that is unambiguous and sufficiently easy to read, they should just be left alone. We should strongly discourage Unit Expression Purity Edit Rampages™ (UEPERs™, pronounced "weepers") as it's just simply not worth people's time and they'd result in a lot of flooding of the front page.


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