Bar / overline (x̄) in LaTeX
The bar accent \bar{x} draws a short horizontal line over a single symbol, most often to denote a sample mean (x-bar) or a complex conjugate. For a bar that spans several symbols use \overline{...} instead.
LaTeX command
\bar{x}Not the symbol you meant? Draw it to find the command →
\bar{x} is a math-mode accent whose bar is sized for one character. It is the standard notation for the sample mean of a data set, and also appears for the complex conjugate of a number and for the complement of a set. It needs no extra package and renders in KaTeX anywhere in math mode.
The key distinction is width. \bar always produces a fixed, narrow bar tuned to a single letter, so \bar{AB} looks wrong because the line is too short. When the bar must cover two or more symbols, a whole expression, or a repeating decimal, switch to \overline{...}, which stretches to fit its contents.
Both commands are purely visual and do not change how the symbol behaves in an equation. Use \bar for one letter and \overline for a group, closure or conjugate of an expression such as \overline{z_1 z_2}. For a line underneath use \underline instead.
Other forms
\overline{x+y}overline over several symbolsExamples
$\bar{x} = \frac{1}{n}\sum_{i=1}^{n} x_i$the sample mean
$\overline{z} = a - bi$complex conjugate over a single symbol
$\overline{z_1 + z_2} = \overline{z_1} + \overline{z_2}$\overline stretches over an expression
$\overline{A \cup B} = \bar{A} \cap \bar{B}$De Morgan with set complements
$0.\overline{3} = \frac{1}{3}$a repeating decimal
Tips and common mistakes
- Use
\bar{x}for one symbol; the moment the bar must cover more than one character, switch to\overline{...}or it will be too short. - Neither
\barnor\overlineneeds a package; both are core LaTeX and are supported by KaTeX. - Mind subscripts:
\bar{x}_ibars the x then adds the index, whereas\overline{x_i}draws the bar over the whole x_i. - For a wide bar over an arc or segment use
\overline; for a directed segment use\overrightarrowinstead. - Do not confuse
\barwith\hator\tilde; each is a different accent but all share the same single-character sizing.
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Convert your maths to LaTeX →FAQ
What is the LaTeX command for x bar (the mean)?
Write in math mode. It renders a short bar over the x, the standard symbol for a sample mean.
How do I put a bar over more than one letter?
Use \overline{...}, for example or . \bar only sizes itself to one character and will look too short over a group.
What is the difference between \bar and \overline?
\bar is a fixed-width accent for a single symbol; \overline stretches to cover whatever is inside its braces. Neither needs an extra package.