Left Right Arrow (Double) in LaTeX (\Leftrightarrow)

Where it is used

Draws a short double-shafted two-headed arrow for logical equivalence between formulas.

\Leftrightarrow states that two formulas imply each other, as in A \Leftrightarrow B. For equivalence between full statements in display math, \iff gives the longer \Longleftrightarrow with extra spacing. Boolean algebra uses it for XNOR or the biconditional. In chains of equivalent equations, aligning a column of \Leftrightarrow with align is a common pattern in solution manuals. Do not confuse it with \equiv, which expresses identity or congruence rather than logical equivalence. Only write it when every step really is reversible; squaring both sides, for example, breaks equivalence.

Also listed under: Logic & Proofs, Boolean Algebra

Minimal compilable example

Paste this into an empty .tex file and compile it with pdfLaTeX, XeLaTeX or LuaLaTeX.

\documentclass{article}
\begin{document}
Left Right Arrow (Double): $\Leftrightarrow$

\[ 2x + 3 = 7 \Leftrightarrow 2x = 4 \Leftrightarrow x = 2 \]
\end{document}

Related symbols

• Long Left Right Arrow (Double)\Longleftrightarrow
• Up Down Arrow\updownarrow
• Up Down Arrow (Double)\Updownarrow
• Long Left Right Arrow\longleftrightarrow
• Maps To\mapsto
• Left Right Arrow\leftrightarrow

Frequently asked questions

How do I write Left Right Arrow (Double) in LaTeX?

Type \Leftrightarrow in math mode, for example $2x + 3 = 7 \Leftrightarrow 2x = 4 \Leftrightarrow x = 2$. It works in plain LaTeX without loading any package.

Which package do I need for \Leftrightarrow?

None. \Leftrightarrow is part of standard LaTeX, so it compiles with nothing in the preamble but the document class.

Can I use \Leftrightarrow in text mode, or only in math mode?

Only in math mode. Outside $...$ LaTeX stops with "Missing $ inserted", so write $\Leftrightarrow$ in running text. If you only need the glyph in text, paste the Unicode character ⇔ instead (with XeLaTeX or LuaLaTeX and a font that has it).