Here is an example:

\usepackage[quotient-mode = fraction]{siunitx}
  \[\SI{1 / 2500 \pi ^ 2}{\micro \farad}\]

It produces:

siunitx error: "invalid-token-in-number"

Thank you for your help in advance!

  • 1
    siunitx expects a number, since it uses a parsing engine. Thus you can't give it stuff it would have to evaluate first. I don't know if there is a way to turn it off, but here you'd probably fare best to git for \[ {1 / 2500 \pi ^ 2}~\si{\micro \farad} \]
    – Timm
    Mar 16, 2017 at 12:31
  • @ Timm I assume that the OP does not want to have it evaluated, but just to get \pi squared ...
    – Jürgen
    Mar 16, 2017 at 12:37
  • @Jürgen: Is assumed that, I intended to use "evaluated" as a more general term for read-and-figure-out-what-it-is. Maybe a question for English Language & Usage ;).
    – Timm
    Mar 16, 2017 at 13:17

1 Answer 1


The number parser can be disabled using

\SI[parse-numbers=false]{1 / 2500 \pi ^ 2}{\micro \farad}

for this single case or generally with

\sisetup{parse-numbers = false}

As to the 'why' part: the package is focussed on physical quantities, and real measurements cannot delivery \pi^2 or similar as an outcome, only (here)

\SI{3.95e-3}{\micro \farad}

or similar

  • 1
    Though of course if you want to compare a measured value with a theoretical prediction, you might well want to typeset them the same - presumably hence why it's possible but not the default.
    – Chris H
    Mar 16, 2017 at 13:42
  • @ChrisH Perhaps though the value you are comparing will still be a real number
    – Joseph Wright
    Mar 16, 2017 at 17:35
  • Personally I use \si instead of \SI in cases like this. Sometimes you do want the units attached to an exact real or irrational value.
    – Chris H
    Mar 16, 2017 at 17:50
  • It would be interesting if the error message mentioned this option. Mar 16, 2017 at 18:52
  • Thank you @Joseph Wright and all other for the answer and comments! When I use parse-numbers = false then is the package option quotient-mode = fraction is disabled. Can I have both things? Thank you for your help in advance!
    – Su-47
    Mar 17, 2017 at 6:22

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