I'm discussing fuel efficiency in liters per 100 kilometers (L/100 km). My first thought was to do the following:

% renders: L/100km

However, that omits the space between 100 and km. Appending whitespace to the end of 100 has no effect, as I expected. However, adding whitespace outside of \num does work:

\si[per-mode=symbol]{\liter\per\num{100} \kilo\meter}}
% renders: L/100 km

But that seems clunky. Is there a better way? Nothing in the docs is catching my eye: ftp://ftp.tex.ac.uk/ctan%3A/macros/latex/exptl/siunitx/siunitx.pdf

  • Remove \num ? But I think what you want is not standard because then it becomes arithmetic in words I would read it as L/100-many kilometers
    – percusse
    Mar 11, 2014 at 20:29
  • @percusse Exact same situation as with \num, unfortunately. I'm open to the idea that this is how you do it, but it seems like there'd be a better way given the depth of the package.
    – Paul H
    Mar 11, 2014 at 20:31
  • I get a space with \liter\per100 \kilo\meter. Note that num puts the contents in mathmode so spaces are ignored. And lastly I would use frac mode with no ambiguity
    – percusse
    Mar 11, 2014 at 20:32
  • @percusse so do I, but that seems equally clunky given how \SI{>> 5}{\metre} renders a space between the 5 and m
    – Paul H
    Mar 11, 2014 at 20:34
  • That's not a unit but the quantity hence the space in between.
    – percusse
    Mar 11, 2014 at 20:36

1 Answer 1


There are at least a couple of ways of handling this. You could simple type things in in literal mode, or you could create a new unit to represent '100 km':


\si{l/100~km} \si[per-mode = symbol]{\litre\per\Ckm}

  • +1, but why not \hkm as hecto-? In my language ckm is a heavy machine-gun. :-) May 29, 2016 at 22:09
  • @PrzemysławScherwentke Roman numeral representation
    – Joseph Wright
    May 30, 2016 at 8:04

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