Online Roman Numeral Converter

Online Roman Numeral Converter

Converts in either direction between ordinary Arabic integers and canonical uppercase Roman numerals using I, V, X, L, C, D and M. Verified 2026 converts to MMXXVI.

Arabic-to-Roman accepts integers from 1 through 3,999. It uses standard subtractive pairs IV, IX, XL, XC, CD and CM; zero, negatives, decimals and values above 3,999 are rejected because overline notation is not implemented.

Roman input is case-insensitive, limited to 32 characters and must be canonical. The parser calculates the value and converts it back for comparison, so nonstandard forms such as IVI are rejected rather than normalized silently.

The page handles modern conventional Roman-number syntax only. It does not support Unicode Roman numeral characters, medieval variants, fractions, clock-face IIII, overbars or historical epigraphic spelling.

Conversion runs locally in the browser. Roman numerals are a notation conversion, not a localized number formatter; the output intentionally remains the Latin symbol set.