I'm trying to typeset an equation that contains a "|":

\lambda_{l} = \lim_{q \to 0^{+}}P\left(X_{2} \leq F_{2}^{(-1)}(q) \middle|  X_{1} \leq F_{1}^{(-1)}(q) \right) 

which gives me enter image description here

The "|" seems to be too long. I've tried \midbut that makes the vertical bar too short in relation to the outer left and right brackets. Is there a way I can get the "right" size "|" automatically?


  • 3
    You really need to include a MWE that recreates the problem. With a bare document with just amsmath loaded, the issue does not present for me.
    – cslstr
    May 29, 2014 at 16:04
  • In particular, as the font you're using clearly isn't Computer Modern, please be sure to indicate which font-related package(s) you load.
    – Mico
    May 29, 2014 at 16:39
  • I'm loading \usepackage[bitstream-charter]{mathdesign} and \usepackage[scaled]{berasans} May 29, 2014 at 16:44

3 Answers 3


I'd argue that not only the middle vertical bar but also the outer parentheses are unnecessarily large. Try using \bigl(, \bigm|, and \bigr) to control the size of the symbols. As an extra nice touch, you could add a thinspace on either side of the big parentheses.

enter image description here

\lambda_{l} = \lim_{q \to 0^{+}}P\bigl(\, X_{2} \leq F_{2}^{(-1)}(q) \bigm|  
    X_{1} \leq F_{1}^{(-1)}(q) \,\bigr) 
  • \delimiterfactor=850 reduces the size of all of \left(, \right) and \middle|. They then actually come out the same size. However, that could possibly ruin other combinations. The real problem seems to be that there are finer divisions between different sizes of parentheses than between different sizes of \middle| in these mathdesign fonts.
    – Dan
    May 29, 2014 at 17:48

use \big| instead. However, for me it looks ok with \middle|.


You can use this definition for conditional probabilities, adapted from the last version of mathtools (p. 27 of the doc). It has a simple syntax: \Prob{A \given B} for a a series \left…\middle…\right, or with an optional size argument: \prob[\big-Big-bigg-Bigg]{A \given B}:




    \lambda_{l} & = \lim_{q \to 0^{+}}\Prob{X_{2} \leq F_{2}^{(-1)}(q) \given X_{1} \leq F_{1}^{(-1)}(q)} \\
     & = \lim_{q \to 0^{+}}\prob[\big]{X_{2} \leq F_{2}^{(-1)}(q) \given X_{1} \leq F_{1}^{(-1)}(q)}

enter image description here

  • this does not work and generates errors
    – pixelou
    Jul 3, 2018 at 13:37
  • @pixelou: Do you have errors with this very code, and nothing else? Which errors?
    – Bernard
    Jul 3, 2018 at 13:58
  • see here: papeeria.com/p/1f7c62db-ff20-4045-b147-fb29d3ed0103#/main.tex "Undefined control sequence. [\end{align}]"
    – pixelou
    Jul 3, 2018 at 14:26
  • @pixelou: I've jsut seen your comment, but the link doesn't work (‘requested project not exists’). However, a simple question: are the fourier package (not mandatory, can be removed from the code: it's a font package) and mathtools (mandatory) installed?
    – Bernard
    Jul 3, 2018 at 16:01
  • yes I have, it looks like a conflict of packages, your example alone actually works fine.
    – pixelou
    Jul 3, 2018 at 18:36

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