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Roman Numeral Converter

Convert between Arabic numbers and Roman numerals instantly

Roman Numeral Converter translates between Arabic numbers and Roman numerals in both directions, with input validation that catches malformed numerals like IC or VV. Type 2026 to get MMXXVI, or paste MDCCCXII to get 1812. Useful for students, tattoo planners, designers, and anyone decoding copyright dates at the end of old movies.

How to Use

  • Choose direction: Convert To Roman or To Arabic.
  • Enter value: Type a number (1-3999) or a Roman numeral.
  • View result: The conversion appears instantly.
  • Copy: Copy the result to your clipboard.

Features

  • Convert numbers to Roman numerals
  • Convert Roman numerals back to numbers
  • Supports the standard range up to 3,999
  • Input validation for malformed numerals
  • Instant, bidirectional conversion

How Roman Numerals Work

The system uses seven symbols — I (1), V (5), X (10), L (50), C (100), D (500), M (1000) — combined by two rules. Numerals placed after a larger or equal numeral add up: VI is 6, XX is 20. A smaller numeral placed before a larger one subtracts: IV is 4, IX is 9, XL is 40, CM is 900. Subtraction is restricted — only I, X, and C can act as the subtracted value, and only from the next two larger symbols — which is why 99 is XCIX, not IC.

There is no zero and no standard symbol beyond the thousands, so 3,999 (MMMCMXCIX) is the practical ceiling. The Romans themselves were inconsistent about these rules, and clock faces famously still show IIII for 4. Today the system survives in movie copyright years, Super Bowl numbering, book chapters, monarch names like Charles III, and clock dials.

Use Cases

  • Converting years for tattoos, engraving, and design work
  • Reading dates carved on buildings and shown in film credits
  • Homework help and teaching number systems
  • Numbering outlines, chapters, and appendices

Frequently Asked Questions

What are Roman numerals?

Roman numerals use letters: I=1, V=5, X=10, L=50, C=100, D=500, M=1000.

Why is the limit 3,999?

Standard Roman numerals don't have a symbol for 5,000 or higher.

Why is 4 written as IV instead of IIII?

The subtractive rule: a smaller numeral before a larger one is subtracted, so IV = 5 - 1. Some clock faces still use IIII by tradition.

Can I convert years?

Yes — years are the most common use. For example, 2026 converts to MMXXVI.