Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers instantly. Supports 1–3999 with subtractive notation, year conversion, extended vinculum notation, and reference table.
Roman Numeral
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Note —
Extended More scenarios, charts & detailed breakdown ▾
Roman Numeral
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Professional Full parameters & maximum detail ▾
Conversion
Roman Numeral (standard) —
Extended (vinculum notation) —
Year Converter
Year in Roman Numerals —
Notation Variants
Additive Form (non-standard) —
Unicode Roman Numerals Note —
How to Use This Calculator
- Enter a number from 1 to 3999 and see the Roman numeral instantly.
- Use Roman to Number tab to convert a Roman numeral string (e.g. MCMXCIX) back to a decimal.
- Use Reference Table to see all 13 base symbols and subtractive notation rules.
- Use the Professional tab for year conversion, extended vinculum notation (4000+), and Unicode characters.
Formula
Subtractive notation: When a smaller symbol precedes a larger one, subtract it: IV = 5−1 = 4, CM = 1000−100 = 900.
Algorithm: Find the largest symbol ≤ remaining value, append it, subtract, repeat.
Example
Convert 2024: 2024 − 1000 = M, 1024 − 1000 = M, 24 − 20 = XX, 4 = IV → MMXXIV.
Convert MCMXCIX: M(1000) + CM(900) + XC(90) + IX(9) = 1999.
Frequently Asked Questions
- Roman numerals use 7 symbols: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Symbols are usually written largest to smallest, left to right. Subtractive notation applies when a smaller symbol precedes a larger one: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.
- In standard notation, MMMCMXCIX = 3,999. The number 4,000 cannot be represented with standard symbols. Extended notation uses a vinculum (overbar) to multiply a symbol by 1,000, allowing much larger numbers.
- Write each part of the year using Roman numeral rules. 2024 = MMXXIV (MM=2000, XX=20, IV=4). 1999 = MCMXCIX (M=1000, CM=900, XC=90, IX=9).
- Subtractive notation allows placing a smaller numeral before a larger one to indicate subtraction. Only specific pairs are valid: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900). Writing IIII for 4 is additive (non-standard today).
- Yes — Unicode block U+2160 to U+2188 contains Roman numeral characters like Ⅰ Ⅱ Ⅲ Ⅳ Ⅴ Ⅵ Ⅶ Ⅷ Ⅸ Ⅹ Ⅺ Ⅻ Ⅼ Ⅽ Ⅾ Ⅿ. These are separate code points from regular ASCII letters.