Hi Peter,
The scale bar is implemented as atoms/bonds and the text is essentially an atom label.  Atom label size (all labels at once) can be set in the Preferences (open from Favorites menu), category: Labels.
<http://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/preferences.html#Labels>

This is mentioned in the Scale Bar “limitations” section at the bottom of the page but is easy to miss…
<http://www.rbvi.ucsf.edu/chimera/docs/ContributedSoftware/scalebar/scalebar.html>

For more control over label size independent of any atom labels, you could make the label blank in in the Scale Bar tool and instead add it as a 2D Label (menu: Tools… Utilities… 2D Label). 2D labels may also include symbols such as the Angstrom symbol.
<http://www.rbvi.ucsf.edu/chimera/docs/ContributedSoftware/2dlabels/2dlabels.html>

I hope this helps,
Elaine
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Elaine C. Meng, Ph.D.
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco

> On Feb 20, 2020, at 4:47 AM, Engelhardt, Peter <peter.engelhardt@helsinki.fi> wrote:
>
> Hi
> We can’t find any options for font size in scale bar wondering if possible.
> Any suggestions
> Cheers
> Peter