Convert between Arabic numbers and Roman numerals instantly — supports 1 to 3,999.
Also convert binary numbers with the Binary Decimal Converter or check character counts with the Character Counter.
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This Roman numeral converter works as a number to Roman numeral translator, Roman numeral decoder, and Arabic to Roman numeral calculator for students, writers, designers, and anyone who needs to convert between the two numeral systems quickly.
The Roman numeral system uses seven symbols: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Numbers are formed by combining these symbols, with larger values placed before smaller ones for addition, and smaller values placed before larger ones for subtraction. This subtractive notation is used for six specific combinations: IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900). The system covers values from 1 to 3,999 — the largest standard Roman numeral, MMMCMXCIX, represents 3,999.
Roman numerals are still widely used today in contexts where a formal or classical appearance is desired. They appear in book chapter numbers, movie sequel titles and copyright years in film credits, clock faces, Super Bowl numbering, Olympic Games numbering, and the names of monarchs and popes. Students encounter Roman numerals in history, classics, and mathematics coursework. Designers use them in logos and headings for a timeless aesthetic. This tool supports both directions of conversion — entering a number returns its Roman numeral equivalent, and entering a Roman numeral string returns the Arabic number — making it useful for both encoding and decoding.
The subtractive notation rule — where a smaller symbol placed before a larger one means subtraction — is one of the most distinctive features of the Roman system compared to purely additive numeral systems. Only six subtractive combinations are valid in standard Roman notation: IV, IX, XL, XC, CD, and CM. Writing IL for 49 or IC for 99, for example, is not standard and would be considered incorrect. The correct forms are XLIX and XCIX respectively. This tool follows the standard rules strictly, so the output is always correct for academic, professional, and creative use.