Personally I think the default size of square brackets in latex math mode is too small. For example, for an interval [a,b], I would prefer \big[\big] as opposed to plain []. My question is, what can I do to change the default size of [], so that when I input [] in math mode, they will show up automatically the same size as \big[\big]?

Right now I'm defining a new command called \b{} which takes one argument and inserts it between \big[ and \big], but the code looks ugly. Apparently \newcommand (or \def or \let) does not allow [ to be refined.

Any help is much appreciated. Thanks.


You can load a scaled version of the relevant font and substitute the standard definitions for [ and ]. Below I have chosen a scaling of 1.2 over the standard size for some exaggeration, probably you only want a factor of 1.1

Sample output






\( [a,b] \)

\left[a,c\right] \bigl[a,b\bigr] \Bigl[a,b\Bigr] \biggl[a,b\biggr] \Biggl[a,b\Biggr]

\( ([()]) \)


The code adjusts the normal size of the brackets, but not the large scaled versions. You would have to apply similar techniques to the largesymbols family to change those.

  • Wouldn't something like \DeclareMathDelimiter{[}{\mathopen} {loperators}{"5B}{largesymbols}{"02} be safer?
    – campa
    May 16 '19 at 8:52
  • @campa Thanks. I think we need both, your code is relevant for \left...\right. May 16 '19 at 9:03
  • Thanks guys I believe that's exactly what I'm looking for!
    – Jason
    May 19 '19 at 7:16

You could define \[ as \big[ and \] as \big], the problem is that \[\] are already defined to open and close the displaystyle math mode environment so one has to undefine them.




  • 2
    What about the already-available \[ \]? The whole document will be messed up. At least one should find a different name for the macro. Redefining one of the most important macro in LaTeX doesn't sound good to me.
    – user156344
    May 16 '19 at 9:40
  • @JouleV Totally agree, but the author wanted something that didn't change the syntax of the parentheses. That's the closest thing that I could think of. May 16 '19 at 17:00

You can define your own command (not \b because it has been already defined) to achieve your objective.


    $[31]$ original\\
    \brakets{31} something something something...\\
    \brakets{xyz} something something something...\\
    $\brakets{xyz} + x = \cdots$ in mathmode as well\\

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