# Roman Numeral Converter Convert between Roman numerals and ordinary numbers in either direction — just type, and the tool detects which way you mean. Runs entirely in your browser. Number → Roman numeral ### How it works If you type digits, the number is built from the standard additive/subtractive symbols (`M`=1000, `CM`=900, `D`=500 … down to `I`=1). If you type letters, each symbol’s value is summed, subtracting when a smaller symbol precedes a larger one. The result is validated by converting it back and checking it matches — so malformed numerals like `IIII` or `VX` are rejected. Classic Roman numerals cover 1 to 3999. --- *Source: [ocxly.com/roman-numeral.html](https://ocxly.com/roman-numeral.html) — OCXLY, free 100% client-side privacy-first tools. Free Roman numeral converter. Convert numbers to Roman numerals and Roman numerals to numbers, with automatic direction detection and validation, entirely in your browser.*