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Convert any number (1 to 3,999) to Roman numerals and Roman numerals back to numbers instantly. Includes a complete conversion table, Roman numeral rules, and interesting historical facts about where Roman numerals are still used today.
Roman numerals were the standard number system used in ancient Rome and throughout Europe until the Middle Ages. Today they are still used for clock faces, movie release years, book chapters, Super Bowl numbers, and formal documents. Understanding the system helps decode these modern uses.
Seven letters represent values: I (1), V (5), X (10), L (50), C (100), D (500), M (1000). Numbers are formed by combining these letters and applying subtractive notation for certain combinations.
When a smaller value precedes a larger value, subtract it: IV = 4 (5-1), IX = 9 (10-1), XL = 40 (50-10), XC = 90 (100-10), CD = 400 (500-100), CM = 900 (1000-100). These are the only valid subtractive combinations.
| Arabic | Roman |
|---|---|
| 1 | I |
| 4 | IV |
| 5 | V |
| 9 | IX |
| 10 | X |
| 40 | XL |
| 50 | L |
| 90 | XC |
| 100 | C |
| 400 | CD |
| 500 | D |
| 900 | CM |
| 1000 | M |
| 2024 | MMXXIV |
| 1999 | MCMXCIX |