Real numbers (ℝ) in LaTeX
\mathbb{R} produces the blackboard-bold symbol for the set of real numbers. The same \mathbb command gives the other standard number sets: N, Z, Q and C.
LaTeX command
\mathbb{R}Not the symbol you meant? Draw it to find the command →
\mathbb{R} renders R in blackboard bold (double-struck), the conventional symbol for the real numbers. The \mathbb font is designed for uppercase Latin letters, so \mathbb{N} (naturals), \mathbb{Z} (integers), \mathbb{Q} (rationals) and \mathbb{C} (complex) all work. In full LaTeX \mathbb comes from the amssymb package; KaTeX supports it natively.
Use blackboard bold only for these standard sets and a few named structures; for an arbitrary set a plain italic letter is more usual. Applying \mathbb to lowercase letters or digits is not part of the standard font and may render inconsistently, so keep it to capitals.
To restrict a set, combine the symbol with ordinary sub- and superscripts: \mathbb{R}^n for n-dimensional space, \mathbb{R}_{>0} or \mathbb{R}^{+} for the positive reals, and \mathbb{Z}^{+} for the positive integers.
Other forms
\mathbb{N}naturals (ℕ)\mathbb{Z}integers (ℤ)\mathbb{Q}rationals (ℚ)\mathbb{C}complex (ℂ)Examples
$f : \mathbb{R} \to \mathbb{R}$a real-valued function
$\mathbb{N} \subset \mathbb{Z} \subset \mathbb{Q} \subset \mathbb{R} \subset \mathbb{C}$the chain of number sets
$x \in \mathbb{R}^n$a point in n-dimensional space
$\mathbb{R}_{>0}$the positive reals
$z \in \mathbb{C}, \ z = a + bi$a complex number
Tips and common mistakes
\mathbbis for uppercase Latin letters only;\mathbb{r}or\mathbb{2}is not standard and may not render as intended.- In full LaTeX load amssymb (or the newer unicode-math) for
\mathbb; KaTeX has it built in, so latexnotes.tech renders it without setup. - For blackboard-bold digits (rare) you need a dedicated package such as bbold; the default
\mathbbdoes not provide them. - Reserve blackboard bold for the standard number systems and named sets; use plain italics for generic sets to avoid confusion.
- Build restricted sets with ordinary sub/superscripts, for example
\mathbb{R}^n,\mathbb{Z}^{+}or\mathbb{R}_{\geq 0}.
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Convert your maths to LaTeX →FAQ
How do I write the real numbers symbol in LaTeX?
Use in math mode. It renders a double-struck (blackboard-bold) R. In full LaTeX this needs the amssymb package.
How do I get N, Z, Q and C?
Use the same command with the matching capital: , , and .
Why does \mathbb not work for lowercase letters?
The \mathbb font only defines uppercase Latin letters, so lowercase input is undefined and renders inconsistently. Blackboard bold is used for capitals such as R and C.