How do I format a physical quantity (unit of measurement + numerical value)?

I tried $I = 1 v / R$ but v looks like a factor rather than unit of measurement. Does tex work in meta?

I use \:\mathrm{<units go here>}

$E=120\:\mathrm{kgm^2s^{-2}}$

gives

I also use this userscript. It lets me enclose stuff with the dollar signs via Alt-M, and Alt-S does \:\mathrm{<selected text here>} for SI units. (there also are options for vector fields and double-dollarifying)

If you want mathjax on meta, upvote MathJax on Meta

• Always posting advertisements..! - a spam user :P – Waffle's Crazy Peanut Apr 27 '13 at 14:17
• I suggest adding a small space between the kg and m^2 for clarity: $E=120\:\mathrm{kg\,m^2s^{-2}}$. – Jason A May 4 '13 at 14:05
• Oops, just noticed the answer by @ChisWhite below, but the small space looks better than either $\:$ or the $\cdot$, by keeping the units grouped a bit compared to the space between number and units IMHO. – Jason A May 4 '13 at 14:12

As a complement to Manishearth's answer, I'll note that there are 4 standard small amounts of space available:

• $\,$ is 3/16 of a "quad" (more or less the width of M, or at least that was the original idea),
• $\:$ is 4/16 of a quad,
• $\;$ is 5/16, and
• $\⊔$ (that's a backslash + space) is something like 6/16 and generally agrees the best with the local interword spacing.

IMO this last option is easiest to type, makes the source look less cluttered, and leads to smoothly flowing spacing. But all options are available.

For multiple units, you probably want to separate implicit multiplications, e.g. $\mathrm{kg\:m/s^2}$ or $\mathrm{kg{\cdot}m/s^2}$.

Besides units, manual spacing most often comes up when separating the "dx" part of the integral, especially for people like me who use upright d's. $\int x^2\ \mathrm{d}x$ tends to render well on this site, though some prefer a smaller space.

\operatorname, \mbox, \mathrm, \text achieve essentially the same purpose.

There's also \fbox (if you want an actual $\fbox{box}$), \mathbf (which achieves this and bolds stuff too) and \bf (essentially the same thing).