What This Tool Does
This tool converts between decimal numbers and Roman numerals in the range 1 to 3999, the range standard Roman numeral symbols can represent. Type into either field and the other updates instantly, along with a visual breakdown showing exactly which symbols were combined to produce the result.
How to Convert a Roman Numeral
Type a number into the Decimal field to see its Roman numeral, or type a Roman numeral into the Roman field to see its decimal value. The breakdown panel on the right shows the symbols that sum to your number, a reference table of every symbol and its value, and the neighbours strip lets you jump to a nearby value with one click.
The Rules That Make a Roman Numeral Valid
I, X, C, and M may repeat up to three times in a row (III = 3, but four in a row is not valid), while V, L, and D never repeat. A smaller symbol placed before a larger one subtracts instead of adds, but only specific pairs are valid: I before V or X, X before L or C, and C before D or M. A string that decodes to a number but does not follow these rules, like IIII or VX, is not a genuine Roman numeral, this tool checks for that rather than just recognizing individual symbols.
Why the Range Is 1 to 3999
Standard Roman numerals have no symbol for zero, and the largest single symbol is M for 1000, meaning three of them (MMM) is the highest value expressible without resorting to non-standard notation like a bar over a symbol to multiply it by 1000. That puts the practical upper limit at 3999 (MMMCMXCIX) for everyday use.
Common Uses for a Roman Numeral Converter
Reading the copyright year at the end of a movie, working out a Super Bowl or Olympic Games number, numbering book volumes or chapters, decoding a clock face or building cornerstone, and designing a tattoo or monogram using Roman numerals for a birth year are all common reasons to use this tool. As a roman numeral translator it can convert number to roman numerals or turn a roman numeral to number, acting as a roman numeral date converter to turn a year to roman numerals, covering the full range of roman numerals 1 to 3999 as a roman numeral generator, a decimal to roman numeral converter, and a quick roman numeral chart.