I am trying to get a Greek omega letter as an Ohm sign in the running text for my paper. I found a solution using siunitx or textgreek here. Unfortunately, the packages are not on the whitelist of ACM that can be found here. Any suggestions on how to solve this problem?

  • 2
    Use the \ohm command from siunitx if it is on the list. You'll get both an upright Ω and a correct spacing with the \SI command
    – Bernard
    Jul 16, 2020 at 11:57
  • As mentioned in my question the package is not on the list.
    – Knall bert
    Jul 16, 2020 at 11:58
  • It has the old SIunits package, though... and that should offer an upright Ω somewhere.
    – Rmano
    Jul 16, 2020 at 12:10
  • 1
    If you are restricted on packages, can you use simply \ensuremath{\Omega}?
    – Joseph Wright
    Jul 16, 2020 at 12:15
  • 1
    You'll probably want to do \newcommand{\ohm}{\ensuremath{\Omega}} to (a) reduce typing and (2) allow you to easily make any necessary adjustments to formatting later.
    – Don Hosek
    Jul 16, 2020 at 14:18

1 Answer 1


You can do this without any packages at all, by taking the symbol from the (default) OT1 encoding.

\usepackage{textcomp}       % Not needed since 2020
\usepackage[utf8]{inputenc} % Not needed since 2018

\DeclareUnicodeCharacter{2125}{\textOmega} % Ohm symbol


Computer Modern font sample

In math mode with amsmath, you’d wrap this in \textnormal. If you want the units to stay upright even when the text is italicized, add \upshape between \fontencoding and \selectfont.

  • These are precisely the kinds of things I'm trying very hard to understand: picking one character from a font, the various encodings and what they actually mean, 8 bit, unicode, etc. Where are these things documented and explained? Jul 16, 2020 at 20:00
  • 1
    @LaTeXereXeTaL The font tables are in the LaTeX Font Encoding Guide, and \DeclareUnicodeCharacter is defined by inputenc and documented there.
    – Davislor
    Jul 16, 2020 at 20:14
  • 1
    @LaTeXereXeTaL The reference to the text font commands is LaTeX2e Font Selection
    – Davislor
    Jul 16, 2020 at 20:15
  • 1
    @LaTeXereXeTaL But for a good user-friendly document, you might go to the `LaTeX Wikibook or Overleaf’s documentation.
    – Davislor
    Jul 16, 2020 at 20:17
  • Okay some of these I'd seen before, but the second one you link to looks to be what I'm looking for. Jul 16, 2020 at 20:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.