Roman Numeral Converter

A movie's copyright year shown as "MCMXCIV" at the end of the credits, a clock face using "IV" instead of "4", or a book chapter numbered "Chapter XII" — Roman numerals still show up often enough that converting them back to ordinary numbers (or the reverse) is a regular small puzzle. This tool converts both directions instantly.

How Roman numerals work

Roman numerals use seven letters as base values (I=1, V=5, X=10, L=50, C=100, D=500, M=1000), combined by addition when a smaller value follows a larger one (like VI = 5+1 = 6), and by subtraction when a smaller value precedes a larger one (like IV = 5-1 = 4). This subtractive notation is what makes reading longer Roman numerals by hand error-prone — this tool applies those rules automatically in both directions.

Where Roman numerals still appear today

Copyright years at the end of films and TV shows, often stylized in Roman numerals. Clock and watch faces, particularly traditional or luxury designs, that use Roman numerals for the hour markers. Formal outlines, book chapters, and legal document sections, which often use Roman numerals for major divisions (I, II, III) before switching to standard numbers for sub-points. Super Bowl and Olympic Games numbering, both of which have used Roman numerals for decades to number each edition.

Frequently Asked Questions

Why is the number field limited to 1-3999? Standard Roman numeral notation using the seven basic letters only cleanly represents numbers up to 3999; numbers beyond that traditionally require special notation (like a bar over a letter to multiply it by 1000) that isn't commonly used in modern contexts.

Does it validate whether I've typed a properly formed Roman numeral? It checks that only valid Roman numeral letters were used and calculates a result using standard rules, though it doesn't flag numerals written in a non-standard order (like "IIII" instead of "IV") as technically incorrect — both would compute to a value, though only the standard form is conventionally correct.

Is my input saved anywhere? No — both conversions run entirely in your browser using JavaScript; nothing is stored or transmitted.