Roman Numeral Converter — Number ↔ Roman, Free Online
Convert between Roman numerals and Arabic numbers. Supports 1 to 3999 with strict canonical form (no IIII). Live validation, uppercase/lowercase output.
Roman Numeral Converter — Convert Numbers Both Ways
Convert between Arabic numbers (1, 2, 3…) and Roman numerals (I, II, III…) in either direction. The tool validates Roman numerals strictly — only canonical forms are accepted (so “IIII” is rejected; the correct form is “IV”). Works for values from 1 to 3999, the standard range of classical Roman numerals.
Roman numeral symbols
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
Subtractive notation
Roman numerals use subtraction for certain combinations:
- IV = 4 (5 – 1), not IIII
- IX = 9 (10 – 1), not VIIII
- XL = 40 (50 – 10)
- XC = 90 (100 – 10)
- CD = 400 (500 – 100)
- CM = 900 (1000 – 100)
Examples
- 2024 = MMXXIV
- 1999 = MCMXCIX (NOT MIM)
- 3999 = MMMCMXCIX (the maximum)
- 1776 = MDCCLXXVI
- 2000 = MM
Why no zero?
The Roman numeral system has no symbol for zero — that concept was introduced to Europe later via Indian/Arabic mathematics. Roman numbers start at I (1).
Why max 3999?
In standard form, you can have at most three Ms in a row (3000). To express 4000+, Romans used a horizontal bar above letters to multiply by 1000, but this is not standard typography. This tool sticks to the strict 1-3999 range.
Common uses
- Movie copyright years (MMXXIV = 2024)
- Book chapter numbers (Chapter IV)
- Outline numbering (I., II., III., IV.)
- Monarch and pope titles (Louis XIV, Pope Francis I)
- Historical date conversion
- Educational quizzes
Privacy
Everything runs in your browser. Your numbers are never uploaded.