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🏛️ Roman Numeral Converter

Convert numbers to Roman numerals and back — with full breakdown, batch mode, and reference table.

Number → Roman Numeral
Roman Numeral
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Roman Numeral → Number
Number
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History
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Reference Table
SymbolValueSymbolValue
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Key Rules
▶ Symbols placed left-to-right, largest first
▶ I, X, C, M can repeat up to 3 times
▶ V, L, D cannot repeat
▶ Subtractive notation: IV=4, IX=9, XL=40…
▶ Valid subtractors: I→V/X, X→L/C, C→D/M
▶ Range: 1 (I) to 3,999 (MMMCMXCIX)
▶ Vinculum (overline) extends to 3,999,999

About Roman Numerals

History

Roman numerals originated in ancient Rome and were used throughout the Roman Empire. Based on letters of the Latin alphabet, they remained Europe's dominant number system until the 14th century when Arabic numerals took over.

Modern Usage

Today Roman numerals appear on clock faces, book prefaces, movie sequels (Rocky IV), Super Bowl numbering, copyright dates (MMXXVI), outlines, monarchs (King Charles III), and Olympic Games years.

Subtractive Notation

When a smaller symbol precedes a larger one it is subtracted: IV = 4 (5−1), IX = 9 (10−1), XL = 40, XC = 90, CD = 400, CM = 900. This avoids IIII, XXXX, CCCC which were also historically valid forms.

Vinculum

A vinculum (overline bar) above a symbol multiplies it by 1,000. V̄ = 5,000, X̄ = 10,000, up to M̄M̄M̄C̄M̄X̄C̄ĪX̄ = 3,999,000. This allows representation beyond 3,999 up to 3,999,999.