Roman Numeral Converter

A free online conversion calculator that convert between roman numerals and arabic numbers instantly. works with values from 1 to 3999, 包括常见数字组合. Get accurate results instantly without any software installation. Roman numerals persist in surprising places: movie copyright dates, book chapter headings, clock faces, royal regnal numbers, sporting event titles like Super Bowl LVIII, and outline structures in academic writing. Translating between Arabic numbers and Roman notation by hand requires memorizing subtractive rules (IV, IX, XL) that trip up even confident users. Enter any number from 1 to 3999 to get its Roman numeral equivalent, or type a Roman numeral to convert back to Arabic. The tool validates subtractive notation rules (IV, IX, XL, XC, CD, CM) and flags invalid combinations. Type any number from 1 to 3999 and the Roman numeral equivalent appears instantly — or paste a Roman numeral and get its Arabic value with validation that flags invalid combinations. The converter handles standard subtractive notation and explains the breakdown of each symbol. Numeral conversion logic runs as pure JavaScript in your browser with no external API calls. This keeps the tool instantly available offline, which is useful in classrooms and exam settings where network access may be restricted.