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Roman Numeral Converter

Convert between decimal numbers and Roman numerals instantly. See a step-by-step breakdown of how the conversion works. Valid range is 1 to 3,999.

Roman numerals are still widely used today in clock faces, book chapters, movie sequels, outlines, and formal documents. Understanding how they work helps you read dates on buildings, decipher Super Bowl numbers, and interpret classical references. This converter handles both directions and shows the exact breakdown of each conversion.

Roman Numeral —
Decimal Number —

Quick Reference

RomanIVXLCDM
Value1510501005001000

Subtractive pairs: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900

About Roman Numerals

The Roman numeral system originated in ancient Rome and was the dominant number system in Europe for nearly two thousand years. It uses seven symbols — I, V, X, L, C, D, and M — combined according to additive and subtractive rules. Additive notation means you add the values of the symbols (e.g., VIII = 5 + 1 + 1 + 1 = 8). Subtractive notation places a smaller symbol before a larger one to indicate subtraction (e.g., IV = 5 - 1 = 4). The standard system can represent numbers from 1 to 3,999. Numbers beyond 3,999 require extended notation with overlines, which is rarely used in modern contexts.

FAQ

What are the rules for writing Roman numerals?
There are three main rules. First, symbols are generally written from largest to smallest, left to right, and their values are added (e.g., XVII = 10 + 5 + 1 + 1 = 17). Second, subtractive notation is used for 4 and 9 patterns: I before V or X (IV=4, IX=9), X before L or C (XL=40, XC=90), and C before D or M (CD=400, CM=900). Third, no symbol is repeated more than three times in a row — you use subtractive notation instead (e.g., IV instead of IIII).
What is subtractive notation in Roman numerals?
Subtractive notation is a shorthand where a smaller-value symbol placed before a larger-value symbol means you subtract the smaller from the larger. For example, IV means 5 minus 1, which equals 4. This avoids writing four identical symbols in a row. Only I, X, and C can be used as subtractive prefixes, and only in specific pairs: IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900).
Why do Roman numerals only go up to 3,999?
The standard Roman numeral system uses seven symbols with M (1,000) as the largest. Since no symbol can be repeated more than three times consecutively, the largest standard Roman numeral is MMMCMXCIX, which equals 3,999. Numbers 4,000 and above historically used an overline (vinculum) to multiply a symbol's value by 1,000, but this notation is rarely used today and is not part of the standard system.
Where are Roman numerals still used today?
Roman numerals remain common in several contexts: clock and watch faces (especially IV and XII), names of monarchs and popes (e.g., Queen Elizabeth II), Super Bowl numbering (e.g., Super Bowl LVIII), book chapters and outlines, copyright year notices on films and broadcasts, and building cornerstones showing the year of construction. They are also used in academic and legal documents for numbering sections and appendices.

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