Roman Numeral Converter

About This Tool

The Roman Numeral Converter converts between Arabic numbers (1–3999) and Roman numerals in both directions. Enter an Arabic number to get the Roman numeral, or type a Roman numeral to get its decimal value. Quick example buttons let you jump to common conversions instantly.

The tool uses the standard subtractive notation: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900. Values below 1 and above 3999 have no standard Roman numeral representation and return an error.

How to Use

1. Select the direction: Arabic → Roman or Roman → Arabic.
2. Enter a number (1–3999) or a Roman numeral (e.g., MMXXIV).
3. Click Convert to see the result.
4. Click any example button for quick common conversions.

Roman Numeral Symbols

I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000. Subtractive pairs: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900. Rules: a symbol may not be repeated more than 3 times consecutively; only one smaller value may precede a larger one.

Use Cases

Students and educators use this tool when studying classical history, Latin, or ancient number systems. Clock and watch enthusiasts decode Roman numerals on watch faces and clock towers. Book publishers and filmmakers encode copyright years in Roman numerals (e.g., MMXXIV = 2024). Puzzle solvers decode Roman numerals in escape rooms, crosswords, and trivia challenges.

FAQ

• What is the largest number in Roman numerals? — Standard Roman numerals go up to 3999 (MMMCMXCIX). Numbers 4000 and above require extensions like a bar over a symbol (vinculum) which are not standard.
• Is IIII valid? — On some clock faces yes, but by strict rules no. Subtractive notation (IV) is standard; IIII is a historical variant.
• What year is MMXXIV? — 2024. MM = 2000, XX = 20, IV = 4.