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Roman Numeral Converter

Convert between Arabic numbers and Roman numerals in real time, with a breakdown of the conversion. Everything runs in your browser.

Last updated: 2026/10/16 Calculator Feedback & bug reports
Result
The converted result will appear here

How to Use

1

Choose a direction

Select the "Arabic → Roman" or "Roman → Arabic" tab.

2

Enter a value

Type a number or a Roman numeral and the result appears instantly.

3

Review and copy

Check the result and breakdown, then copy it to your clipboard with one click.

Basic Roman Numeral Symbols

Roman Value Name
I1one
V5five
X10ten
L50fifty
C100hundred
D500five hundred
M1000thousand

About the Roman Numeral Converter

An online tool that instantly converts between Arabic numbers (1, 2, 3…) and Roman numerals (I, II, III…). It shows a step-by-step breakdown, making it useful for learning how Roman numerals work. All processing happens in your browser, so your input is never sent to any server.

Overline Notation (Numbers Above 3999)

Standard Roman numerals cannot express values of 4000 or more with single letters, but placing a bar (overline) above a symbol multiplies it by 1000. For example, a bar over "V" means 5000, and over "X" means 10000. This tool covers the standard range of 1–3999.

Features

  • Real-time Two-way ConversionConvert Arabic ⇄ Roman as you type, with no waiting.
  • Conversion BreakdownSee exactly which symbol maps to which value in a clear table — great for learning.
  • Automatic ValidationDetects out-of-range numbers and invalid Roman numerals with clear guidance.
  • Privacy ProtectedAll processing happens in your browser. Nothing is sent to a server.

Use Cases

  • Reading clock faces and movie release years in Roman numerals
  • Numbering book chapters and preface pages
  • Studying history, Latin, and mathematics
  • Using Roman numerals in design and logos
  • Checking regnal numbers of kings and popes (e.g. Louis XIV)

FAQ

Is the Roman numeral converter free?
Yes, it is completely free. No registration or installation required — just open it in your browser.
Why does it only convert up to 3999?
In standard Roman numerals a base symbol (M = 1000) is repeated at most three times, so the maximum is 3999 (MMMCMXCIX). Values of 4000 and above require special notation such as the overline.
Do Roman numerals have a zero?
No, Roman numerals have no symbol for zero. That is why only integers of 1 or greater can be converted.
Which is correct, "IIII" or "IV"?
The subtractive form "IV" is standard. "IIII" is sometimes used by convention (e.g. on clock faces), but this tool uses the standard subtractive notation (IV, IX, XL, XC, CD, CM).
Is my input sent to a server?
No, all conversion happens locally in your browser. Your input is never sent to or stored on any server.

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Related Guides

How to Read Roman Numerals: Meaning of I V X L C D M and the Rules Learn how to read Roman numerals from the basics: what the seven letters I, V, X, L, C, D, and M mean, the additive and subtractive rules (IV=4, IX=9), how to write large numbers, use on clocks and in years, tips for converting to Arabic numerals, and why you cannot write 4000 or more.