Chemical formula can look ambiguous with most sans-serif fonts, e.g. Cl (chlorine) can be confused with CI (carbon iodine).

Ideally, a font would have a hook on the "l", and bars on the "I" (apologies for incorrect terminology), many of the fonts in similar questions only have one or the other.

I'm looking for either:

  • a font that disambiguates both "I" and "l", but is otherwise as sans-serif as possible;
  • or, a semi-serif font that will not clash with a different sans-serif font that I can use for the rest of the body text.

The best I've seen so far is Roboto Slab but it unfortunately clashes with the Helvetica that surrounds it, and is too serif-y to use everywhere.

4 Answers 4


From "American Chemical Society Style Guide" for authors [1, pp. 356-357]:

The font (or typeface) is the style or design of the letters. There are literally hundreds of fonts, but plain, simple fonts such as Helvetica or Times Roman are best for scientific art. [...]

Use a clear type font, preferably Helvetica or Times Roman.

The software behind a font is covered by copyright law. Whereas some copyright holders allow open access to their fonts, others exercise some sort of limit. Publishers respect the copyright on fonts and will not use a font without proper permission. [...]

TrueType is a font format designed by Microsoft for maximum legibility on a computer monitor, and it prints well on dot-matrix, inkjet, and laser printers. Microsoft permits free use of the fonts it provides (such as Times New Roman and Arial), but other companies that provide TrueType fonts may have use restrictions. TrueType fonts perform well in Web publishing, but they often pose technical problems in print publishing. TrueType fonts are fine for producing GIFs, TIFFs, and JPEGs, as well as PDFs intended for the Web.

PostScript is a font format designed for high-end graphic arts. These fonts are designed for maximum legibility on paper and for maximum compatibility with high-quality, high-output printing equipment. PostScript fonts are generally covered by copyright and have limitations on their use. They seldom pose technical problems in print publishing, but the copyright issues may limit their usefulness in Web publishing. PostScript fonts are best for EPS files and PDFs intended for print.

OpenType fonts are a relatively new format intended to combine the virtues of both TrueType and PostScript fonts.

STIX (scientific and technical information exchange) fonts were developed by a group of six scientific publishers to establish a comprehensive set of fonts that contains essentially every character that might be needed to publish a technical article in any scientific discipline. STIX fonts are available as a free download, under license, at www.stixfonts.org.

Good old Times New Roman indeed works quite decent, whereas Arial and Helvetica are probably one of the worst possible fonts for chemical formulas. STIX font family is nearly ideal, especially when you use (Xe)LaTeX. I personally like Linux Libertine and very similar Liberation Serif fonts, which are free and often pre-installed on various systems. The bottomline is, don't use exotic and/or non-free fonts, there are plenty to choose from.

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  1. The ACS Style Guide: Effective Communication of Scientific Information, 3rd ed.; Coghill, A. M., Garson, L. R., Eds.; American Chemical Society; Oxford University Press: Washington, DC; Oxford; New York, 2006. ISBN 978-0-8412-3999-9.

What you want is a "schoolbook", "infant" or "textbook" font. Annoyingly, neither Helvetica Textbook nor AG Schoolbook is perfect for what you want: HT has no serif on the lower-case "L" and AGS (which is quite expensive, too) has an odd capital 'i' based on blackletter. This one might work. If you'd consider mixing fonts, you can mix the cap 'i' from Verdana and LC 'L' from Trebuchet. They blend fine in regular, although it does't work in bold where Verdana is much bolder.

  • Many thanks. Ideally I'm looking for a (preferably free) webfont, I'm not sure mixing fonts would be ideal in this case, this is for edu use
    – Matthew
    Commented Oct 5, 2017 at 22:43
  • Fiendstar that you linked looks like a good candidate actually, it doesn't seem prohibitively expensive, though any for-pay-font is going to be difficult for me to justify (sadly)
    – Matthew
    Commented Oct 5, 2017 at 22:56
  • Knew there was an answer: Andika from SIL. Four weights, has all the forms you need, superscripts and subscripts. The one snag is that the LC 'L' you want is an alt character (so is the conventional double-storey 'a') but you could use FontForge (also free) to swap the glyphs into the default position.
    – Copilot
    Commented Oct 5, 2017 at 23:47

Before, I found it hard to make a good recommendation. But fortunately there is a new ideal contender: IBM Plex Sans. This open-source sans-serif has everything you need: a clearly distinguishable 1, lower-case L and upper-case i. It also has an extensive choice of weights. I would call it fairly neutral and able to blend with more or less anything.

  • Marking this as accepted because it seems ideal! Thanks very much :-) (and to everyone else who made suggestions!)
    – Matthew
    Commented Nov 20, 2017 at 3:20

Let's assume you have found the optimal font - so good for this purpose that you pay the premium price for it. You will meet the following problem:

Others cannot have your texts without font substitutons in other form than as images, because the font is only in your PC and you have no right to distribute it nor include it to a document file as embedded.

That can be ok, but if it isn't you must use widely available system fonts or a free font.

There's a workaround: Take a 100% free font and edit the problematic glyphs to fit. It shouldn't be a big deal in a font editor. See an example:

enter image description here

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