Converters
Roman Numeral Converter
Convert numbers to Roman numerals and back — with validation of proper numeral form.
Number → Roman
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Roman → number
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Standard Roman numerals cover 1–3999 (I to MMMCMXCIX).
About this tool
Tattoo dates, clock faces, movie sequels, outline numbering — Roman numerals persist everywhere. Convert any number from 1 to 3999 into its numeral, or decode a numeral back to a number, both directions live.
The decoder validates properly: malformed input like "IIII" or "VX" is flagged as invalid rather than silently misread — important when the numeral is going on skin or in print.
How to use
- Type a number (1–3999) on the left for its Roman numeral.
- Or type a numeral on the right to decode it.
- Invalid numerals are flagged immediately.
Frequently asked questions
MMXXVI — MM (2000) + XX (20) + VI (6).
Standard notation has no symbol beyond M (1000) and repeats a symbol at most three times; larger numbers historically used an overline, which plain text can't show.
Subtractive notation: a smaller symbol before a larger one subtracts. IV = 5−1. (Clock faces sometimes use IIII purely for visual balance.)