HTML Entity for Uppercase R Double Struck Capital (ℝ)

Beginner
⏱️ 5 min read
📚 Updated: Jun 2026
🎯 1 Code Example
Unicode U+211D
HTML Entity for Uppercase R Double Struck Capital tutorial illustration

What You'll Learn

How to display the uppercase R double struck capital (ℝ) in HTML using named entity, hexadecimal, decimal, and CSS escape methods. This mathematical symbol denotes the set of real numbers, commonly written as ℝ in equations such as x ∈ ℝ. It is U+211D in the Letterlike Symbols block (U+2100–U+214F).

Render it with ℝ, ℝ, ℝ, or CSS escape \211D. The named entity ℝ is often the most readable option in HTML source. Do not confuse with ℜ (ℜ, real-part operator). See also math entities.

⚡ Quick Reference — Uppercase R Double Struck Capital Entity

Unicode U+211D

Letterlike Symbols

Hex Code ℝ

Hexadecimal reference

HTML Code ℝ

Decimal reference

Named Entity ℝ

Most readable option

Reference Table
Name           Value
────────────   ──────────
Unicode        U+211D
Hex code       ℝ
HTML code      ℝ
Named entity   ℝ
CSS code       \211D
Meaning        Double-struck capital R (real numbers)
Related        U+211C = ℜ (ℜ, real-part operator)
Block          Letterlike Symbols (U+2100–U+214F)
1

Complete HTML Example

A simple example showing the uppercase R double struck capital (ℝ) using hexadecimal code, decimal HTML code, the named entity, and a CSS content escape:

html
<!DOCTYPE html>
<html>
<head>
 <style>
  #point:after{
   content: "\211D";
  }
 </style>
</head>
<body>
<p>Symbol (hex): &#x211D;</p>
<p>Symbol (decimal): &#8477;</p>
<p>Symbol (named): &Ropf;</p>
<p id="point">Symbol (CSS): </p>
</body>
</html>
Try it Yourself

🌐 Browser Support

The uppercase R double struck capital (ℝ) and the named entity &Ropf; are supported in all modern browsers:

Chrome1+
Firefox1+
Safari1+
Edge12+
Opera4+
Android4.4+
iOS Safari1+

👀 Live Preview

See the uppercase R double struck capital (ℝ) in mathematical notation:

Large glyphℝ
Set notationℚ ⊂ ℝ ⊂ ℂ
Named entity&Ropf; renders as ℝ
Not the same asplain R (U+0052)  |  ℜ (&real;, real part)
Numeric refs&#x211D; &#8477; &Ropf; \211D

🧠 How It Works

1

Hexadecimal Code

&#x211D; uses the Unicode hexadecimal value 211D to display the character. The x prefix indicates hexadecimal format.

HTML markup
2

Decimal HTML Code

&#8477; uses the decimal Unicode value 8477 to display the same character. A common method for Letterlike Symbols.

HTML markup
3

Named Entity

&Ropf; is the standard named entity for ℝ—readable in source HTML and part of the HTML5 entity set for blackboard bold letters.

HTML markup
4

CSS Entity

\211D is used in CSS stylesheets, particularly in the content property of pseudo-elements like ::before and ::after.

CSS stylesheet
=

Same visual result

All four methods produce the glyph: ℝ. Unicode U+211D sits in Letterlike Symbols. Do not confuse with plain R (U+0052) or ℜ (real-part operator). Use math-friendly fonts for best rendering.

✅

Use Cases

The uppercase R double struck capital (ℝ) is commonly used in:

🔢 Real numbers

Denote the set of real numbers ℝ in algebra, analysis, and calculus.

📊 Set theory

Represent number sets alongside ℕ, ℤ, and ℚ.

📚 Education

Textbooks, online courses, and tutorials explaining number systems and blackboard bold notation.

📄 Academic publishing

Research papers, theses, and journal articles in mathematics, physics, and engineering.

💻 Web math tools

Equation editors, calculators, and interactive math apps that render set notation in HTML.

🔬 Scientific docs

Technical documentation and formulas involving fields, limits, continuity, and real analysis.

📝 Technical writing

API docs, developer guides, and content explaining mathematical concepts involving real-valued data.

💡 Best Practices

Do

  • Use &Ropf; in HTML when possible for readability
  • Serve pages as UTF-8; you can also type ℝ directly in UTF-8 source
  • Use math-friendly fonts (e.g. Cambria Math, STIX Two Math) for clear double-struck rendering
  • Distinguish ℝ (set of reals) from ℜ (real-part operator) and plain R (U+0052)
  • Use fonts that support Letterlike Symbols characters

Don’t

  • Substitute plain R when ℝ is required for correct mathematical notation
  • Confuse ℝ (double-struck set) with ℜ (&real;, real-part operator)
  • Put CSS escape \211D in HTML text nodes
  • Use \0211D in CSS—the correct escape is \211D
  • Omit UTF-8 encoding on pages with mathematical symbols

Key Takeaways

1

Four references render ℝ; named entity is most readable

&#x211D; &#8477; &Ropf;
2

For CSS stylesheets, use the escape in the content property

\211D
3

Unicode U+211D — DOUBLE-STRUCK CAPITAL R

4

Essential for real numbers, set theory, and mathematical content

5

Previous: Uppercase R Double Grave (Ȑ)   Next: Uppercase R Inverted Breve

❓ Frequently Asked Questions

Use &Ropf; (named), &#x211D; (hex), &#8477; (decimal), or \211D in CSS content. The named entity &Ropf; is the most readable for HTML content.
U+211D (DOUBLE-STRUCK CAPITAL R). Letterlike Symbols block. Hex 211D, decimal 8477. Commonly used to represent the set of real numbers.
When writing mathematical content, set theory, analysis, academic papers, scientific documentation, educational materials, and any text requiring blackboard bold R notation for real numbers.
HTML code (&#8477; or &#x211D;) or the named entity &Ropf; is used in HTML content. The CSS entity (\211D) is used in CSS, e.g. in the content property of pseudo-elements. Both produce ℝ but in different contexts.
The uppercase R double struck capital (ℝ) represents the set of real numbers. It is used alongside other blackboard bold sets such as ℕ (natural numbers), ℤ (integers), and ℚ (rationals). Do not confuse with ℜ (&real;, real-part operator).

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About the author

Mari Selvan M P
Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

  • Experience 12 years building web and cloud systems
  • Focus Full Stack Development, AWS, and Developer Education

I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

AWS Certified Developer – Associate (Credly)

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