Roman Numeral Converter
Convert numbers to Roman numerals and decode Roman numerals back to numbers.
Standard Roman numerals run from 1 (I) to 3999 (MMMCMXCIX), using the subtractive forms IV, IX, XL, XC, CD and CM. Decoding is strict — an input only converts if it is a well-formed numeral, so typos like “IIII” are flagged. Runs entirely in your browser.
How to convert Roman numerals
Choose Number → Roman or Roman → Number, then type your value. The result appears instantly below — for example 2024 becomes MMXXIV, and MMXXIV decodes back to 2024. Click Copy result to grab it.
Where Roman numerals appear
Copyright years, clock faces, book chapters, Super Bowl and monarch numbering, and film credits all use Roman numerals. Converting both ways makes it easy to read or write them correctly.
Questions
What range of numbers is supported?
Standard Roman numerals cover 1 to 3999, written I to MMMCMXCIX. Above that, numerals require overline notation that isn't part of the everyday system, so the converter keeps to the standard range.
Does it use the subtractive forms?
Yes. It writes 4 as IV and 9 as IX (and likewise XL, XC, CD and CM) rather than the additive IIII, producing the canonical modern numerals.
What happens if I type an invalid numeral?
Decoding is strict: the input only converts if it's a well-formed numeral. Malformed sequences such as IIII or VX are rejected with a clear message instead of a wrong number.