Double-Struck Text Generator
Type text and get it back in double-struck, or blackboard bold, letters and digits — 𝕝𝕚𝕜𝕖 𝕥𝕙𝕚𝕤 — with the seven capitals Unicode keeps in an older block (ℂ ℍ ℕ ℙ ℚ ℝ ℤ) placed correctly. Below the converter, copy the number-set symbols mathematicians use, each with its LaTeX command. Free, no sign-up.
Results
Double-struck (𝕓𝕝𝕒𝕔𝕜𝕓𝕠𝕒𝕣𝕕 𝕓𝕠𝕝𝕕)
Type above to see the result.
ℂ ℍ ℕ ℙ ℚ ℝ ℤ come from Unicode's older Letterlike Symbols block, which is where they have always been encoded. In some fonts they look a little different from the other letters.
Blackboard-bold symbols
Select a symbol to copy it. The LaTeX command is shown below each one.
Screen readers may announce these as math symbols ("double-struck capital R") or skip them, and search treats them as different characters from ordinary letters — fine for mathematics, poor for prose people need to read.
How to Use the Double-Struck Text Generator
- Type or paste your text. Every letter A–Z and a–z and every digit 0–9 is converted as you type. Anything else — accented letters, punctuation, spaces — stays as it is.
- Copy the result. Press Copy and paste the double-struck text into a document, a message or a post.
- Copy a single symbol. For ℝ, ℕ, 𝔼 and the other common symbols, select it in the symbol grid to copy just that character.
- Use LaTeX when you are typesetting. Each symbol shows its LaTeX command, such as
\mathbb{R}, for papers and problem sets you compile rather than paste.
Blackboard Bold in Mathematics
Double-struck letters began as a chalkboard habit. Bold type is impossible with chalk, so lecturers doubled one stroke of a letter to show that it was meant to be bold, and the doubled letters moved from the board into print. Today the double-struck capitals name the standard number systems, and a handful more have fixed meanings in particular fields:
| Symbol | Meaning | LaTeX | Note |
|---|---|---|---|
| ℕ | Natural numbers | \mathbb{N} | Whether 0 is included depends on the author; ISO 80000-2 includes it. Write ℕ0 or ℤ>0 to remove any doubt. |
| ℤ | Integers | \mathbb{Z} | From the German Zahlen, "numbers". |
| ℚ | Rational numbers | \mathbb{Q} | Q for quotient: every rational number is a ratio of two integers. |
| ℝ | Real numbers | \mathbb{R} | ℝn is n-dimensional real space. |
| ℂ | Complex numbers | \mathbb{C} | Numbers a + bi with a and b in ℝ. |
| ℍ | Quaternions | \mathbb{H} | After William Rowan Hamilton, who described them in 1843. |
| ℙ | Primes, probability or projective space | \mathbb{P} | The meaning depends on the branch of mathematics. |
| 𝔼 | Expected value | \mathbb{E} | As in 𝔼[X] in probability and statistics. |
| 𝔽 | A field | \mathbb{F} | 𝔽q is the finite field with q elements. |
| 𝟙 | Indicator function | \mathbbm{1} | Needs the bbm package; the dsfont package writes it \mathds{1}. |
Why Seven Capitals Come From a Different Block
Unicode added the full double-struck alphabet in version 3.1 in 2001, in the Mathematical Alphanumeric Symbols block: capitals from U+1D538, small letters at U+1D552–U+1D56B and digits at U+1D7D8–U+1D7E1. Seven capitals already existed. ℂ (U+2102), ℍ (U+210D), ℕ (U+2115), ℙ (U+2119), ℚ (U+211A), ℝ (U+211D) and ℤ (U+2124) had been in the Letterlike Symbols block since Unicode's first versions, because they were already in everyday use. Rather than encode them twice, Unicode left their slots in the new block empty — U+1D53A, where ℂ would sit, is an unassigned hole — so a correct converter has to reach back to the older characters for those seven letters.
The generator does this for you: typing CHNPQRZ gives ℂℍℕℙℚℝℤ, while every other capital comes from the newer block. Choose Try a sample and Sets N, Z, Q, R and C becomes 𝕊𝕖𝕥𝕤 ℕ, ℤ, ℚ, ℝ 𝕒𝕟𝕕 ℂ — five of the seven exceptions in one line. A converter that simply adds an offset to every capital produces unassigned code points for those letters instead, which typically show up as empty boxes.
Letterlike Symbols also holds double-struck characters that have no key to type them from: the italic ⅅ ⅆ ⅇ ⅈ ⅉ that some notations use for the differential and for e, i and j, the Greek ℾ ℿ ℽ ℼ, and the summation sign ⅀. Copy them from this paragraph if you need one.
Writing Double-Struck Letters in LaTeX
In LaTeX, load the amssymb package (or amsfonts) and write \mathbb{R} in math mode. The AMS font covers capital letters only; \Bbbk gives a double-struck k, and the bbm and bbold packages add lowercase letters and digits, as in \mathbbm{1}. With XeLaTeX or LuaLaTeX and the unicode-math package, \mathbb{R} produces U+211D — the same character this generator outputs — and you can paste ℝ straight into an equation.
A note on accessibility
In a formula, ℝ is the right character, and math-aware software can name it. Used for decoration, double-struck text has the problems of every Unicode style: screen readers may announce each letter by its symbol name or skip it, and search, spell check and translation tools don't recognize the words. Keep it for mathematics and short decorative touches.
Frequently Asked Questions
- What is double-struck text?
- Letters drawn with one stroke doubled, also called blackboard bold. In mathematics the double-struck capitals name the number systems — ℕ, ℤ, ℚ, ℝ and ℂ. Unicode encodes a complete double-struck alphabet and digits, so the style can be pasted as plain text anywhere.
- How do I type the real numbers symbol ℝ?
- Copy it from the symbol grid above. In LaTeX write
\mathbb{R}with the amssymb package. In HTML useℝ,ℝorℝ. In Word, type 211D and press Alt+X; on a Mac, open the Character Viewer with Control+Command+Space and search for "double-struck". - Why do ℂ, ℍ, ℕ, ℙ, ℚ, ℝ and ℤ look slightly different from the other letters?
- They come from the Letterlike Symbols block, encoded years before the rest of the double-struck alphabet, and some fonts draw the two blocks in different designs. They are still the correct and only double-struck forms of those letters — the matching positions in the newer block are deliberately empty.
- Can I get double-struck lowercase letters and digits?
- Yes. Unicode encodes 𝕒 to 𝕫 and 𝟘 to 𝟡, and the generator converts both. LaTeX's standard
\mathbbdoes not include them; use the bbm or bbold package in LaTeX, or paste the Unicode characters with unicode-math. - Does ℕ include zero?
- It depends on the convention. The international standard ISO 80000-2 defines ℕ as {0, 1, 2, …}, and computer science usually follows it, while many number theorists start at 1. When it matters, write ℕ0 or ℤ≥0 for the set with zero and ℤ>0 for the positive integers.
- Will double-struck text display everywhere?
- On current phones, computers and browsers, yes — their math fonts cover the whole block. Older systems may show boxes for the newer letters while still showing ℝ and ℕ, which have been supported far longer. Check on a second device before relying on it.