When I try to produce a = sign in math mode using newtxmath, I get the following error (using pdflatex with TeXLive 2014 on Windows)

ERROR: Font \csname\endcsname=zxxrl7z at 10.0pt not loadable: Metric (TFM) file not found.

Here is a minimal example:


However, if I remove the $ signs I get the right output (i.e., a = sign, but not in math mode, of course). Do I need to enable specific options for newtxmath to get an = sign in math mode?

PS: I have tried including various ams packages, such as amsmath, amssymb, amsfonts etc., but the problem persists.

  • The zxxrl7z font is part of the boondox suite that is required by newtxmath. In TeX Live it's the boondox package, included in collection-fontextra. Install it with tlmgr
    – egreg
    Sep 12, 2014 at 22:16
  • @egreg: That works, thanks! Would you mind adding it as an answer?
    – Piyush
    Sep 12, 2014 at 22:23

1 Answer 1


The newtxmath fonts are virtual fonts that use several other freely available fonts. In particular zxxrl7z is used by ntxmia.vf (composed with pieces from nine fonts) which is the symbol font lettersA. The zxxrl7z font supplies the double struck letters and digits.

The TeX Live distribution doesn't provide a tree of dependencies, unfortunately. The required font belongs to the TeX Live boondox package, which is part of collection-fontsextra. Install boondox with tlmgr

tlmgr install boondox

or, even better, the whole collection

tlmgr install collection-fontsextra

Installing the whole TeX Live is usually the best option.

  • I believe collection-fontextra should be collection-fontsextra (note the s after font): this is the name of the collection in TeXLive 2014. (I cannot submit this as an edit because it is too small in terms of the number of characters).
    – Piyush
    Sep 12, 2014 at 22:40
  • You're right, I'll fix it.
    – egreg
    Sep 12, 2014 at 22:41

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