Convert any Arabic number from 1 to 3,999 to its Roman numeral equivalent in real time. Type a number and the Roman numeral appears immediately. The converter validates the range and shows an error for numbers outside 1–3,999. All conversion runs locally in your browser.
To convert a number to Roman numerals, the tool repeatedly subtracts the largest possible Roman numeral value from the number and appends the corresponding symbol (including subtractive pairs like IV=4, IX=9, XL=40, XC=90, CD=400, CM=900). To convert Roman numerals to a number, each character is mapped to its value; a character is subtracted if the next character has a greater value. All processing runs in JavaScript in your browser.
All conversions happen locally in your browser tab. Our servers are not involved at any point.
For working with fractional or mixed numbers, try the fraction calculator. To convert numbers between binary, hex, and decimal, use the number base converter. For unit conversions like inches to centimetres, see the unit converter.