Roman Numeral Converter — Free Online Tool

The Roman Numeral Converter translates numbers into Roman numerals and back, following the standard subtractive rules.

The system uses seven letters — I, V, X, L, C, D, M for 1, 5, 10, 50, 100, 500, 1000 — combined additively, with a subtractive shortcut for the cases just below a higher value: IV for 4, IX for 9, XL for 40, XC for 90, CD for 400, CM for 900. The rule people most often break is repetition: the same symbol appears at most three times consecutively, which is why 4 is IV and not IIII, and 40 is XL and not XXXX.

Subtraction also has constraints that keep the notation unambiguous. Only I, X, and C are used subtractively, and only before the next two higher values — so 99 is XCIX rather than the intuitive-looking IC. Getting this wrong is the most common source of incorrectly formed numerals, including on a surprising number of published items.

The system has no zero and no standard way to write fractions or negative numbers, which is a substantial part of why positional notation replaced it for calculation. Its survival is entirely conventional: monarchs and popes, film copyright dates, book preface pagination, clock faces, sporting events, and building inscriptions.

The one well-known deliberate exception: clock faces often use IIII rather than IV for visual balance against the VIII opposite it, a convention that has persisted for centuries despite being technically incorrect.

Conversion happens instantly in your browser.

Our Roman Numeral Converter is completely free to use with no signup required. For this tool, processing runs in your browser — your files and data stay on your device and are not uploaded to our servers.

Whether you are a developer, designer, student, or business owner, this tool is designed to save you time and make your workflow more efficient. Bookmark this page to access it whenever you need it — it will always be free.