LaTeX Questions Answered: How Do I Make Brackets Around an Expression Bigger?

The following is an excerpt from the chapter LaTeX Questions Answered in Pressbooks Guide: A reference for open textbook authors using Pressbooks by Lauri M. Aesoph

For our purposes, “brackets” refers to (parentheses), [square brackets], {curly brackets}, and〈angle brackets〉, as well as |vertical bars or pipes| and ||double pipes||.

There may be times when you want your brackets to appear larger than the standard size, such as when you have brackets around a fraction. Luckily, it is very easy to make your brackets match the size of whatever they are trying to contain.

Use the commands \left and \right to create brackets that will resize themselves to match what they surround.

For example, say you want to put parentheses around a fraction. If you use regular parentheses, the expression looks like this:[1]

mathematical equation that shows 3x +4 over 2 (fraction). There are brackets around this by they do not fully encompass the equation

As you can see, the expression isn’t properly contained by the parentheses. Here’s what it looks like when you write \left( and \right) around the expression:

the brackets now fully enclose the fractional equation

Just like that, the parentheses have resized themselves to fit around the fraction.

These dynamic brackets are not always necessary: if your bracketed expression is just a few alphanumeric characters, regular brackets will probably work just fine. But these commands are very useful for when you have a larger expression that you’d like to contain in brackets.

See the following table to learn how to write all the different kinds of brackets.

BracketLaTeX MarkupRendered
[Square brackets][a-b][a−b]
{Curly brackets}\{a-b\}{a−b}
〈Angle brackets〉\langle a-b \rangle⟨a−b⟩
|Vertical bars or pipes||a-b||a−b|
||Double pipes||\|a-b\|∥a−b∥

Now let’s see how to write each type of dynamic bracket:

BracketLaTeX MarkupRendered
[Square brackets]\left[\dfrac{a}{b}\right][ab]
{Curly brackets}\left\{\dfrac{a}{b}\right\}{ab}
〈Angle brackets〉\left\langle\dfrac{a}{b}\right\rangle⟨ab⟩
|Vertical bars or pipes|\left|\dfrac{a}{b}\right|∣∣ab∣∣
||Double pipes||\left\|\dfrac{a}{b}\right\|∥∥ab∥∥

For those types of brackets that require a command of their own and can’t just be written as is — such as the curly brackets, which must be written as \{x\} — the syntax of the \leftand \right commands can start to look a little confusing, especially when combined with other commands.

Just remember that the syntax goes \leftsymbol for the opening bracket\rightsymbol for the closing bracket.

Learn more:

The featured image for this post (viewable in the BCcampus News section at the bottom of our homepage) is by Monstera on Pexels

  1. You can right-click this expression and go to Math Settings > Math Renderer > Plain Source and then back to Common HTML to switch between seeing the original LaTeX markup and the expression in display form.