Real Numbers in LaTeX (\mathbb{R})

Where it is used

Blackboard-bold R, the set of real numbers that make up the continuous number line.

\mathbb{R}^n is Euclidean space, f : \mathbb{R} \to \mathbb{R} a real function, and \mathbb{R}_{\ge 0} or \mathbb{R}_+ the nonnegative reals (conventions differ on whether \mathbb{R}^+ includes 0). Matrix spaces are written \mathbb{R}^{m \times n}. The extended reals are \overline{\mathbb{R}} or [-\infty, \infty]. Avoid \Re, which prints a fraktur R for the real part of a complex number, not the set of reals. Many authors define a short macro \R. Its completeness, every bounded set having a supremum, is what separates it from \mathbb{Q}.

Minimal compilable example

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

\documentclass{article}
\usepackage{amssymb}
\begin{document}
Real Numbers: $\mathbb{R}$

\[ f : \mathbb{R}^n \to \mathbb{R}, \quad x \mapsto \|x\|^2 \]
\end{document}

Related symbols

• Complex Numbers\mathbb{C}
• Rational Numbers\mathbb{Q}
• Power Set\mathcal{P}
• Integers\mathbb{Z}
• Cardinality|A|
• Natural Numbers\mathbb{N}

Frequently asked questions

How do I write Real Numbers in LaTeX?

Type \mathbb{R} in math mode, for example $f : \mathbb{R}^n \to \mathbb{R}, \quad x \mapsto \|x\|^2$. Load amssymb first with \usepackage{amssymb}.

Which package do I need for \mathbb{R}?

\mathbb{R} needs amssymb: add \usepackage{amssymb} to your preamble before the document starts.

Can I use \mathbb{R} in text mode, or only in math mode?

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