Free Online Roman Numeral Converter

1. Pick the direction: Number → Roman or Roman → Number.
2. Type the value into the input box.
3. Read the converted result — invalid inputs surface a clear error message.

The seven Roman symbols are I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Symbols add when in non-increasing order (VII = 7) and subtract when a smaller symbol precedes a larger one (IV = 4, IX = 9, XL = 40). The standard system represents whole numbers from 1 to 3999 — larger values require a vinculum (overline) most fonts can't render, so MMMCMXCIX (3999) is the practical upper bound. There is no Roman numeral for zero or for negative numbers.

Roman numerals survive today on clock faces, in chapter numbering, on movie copyright dates, and in the names of monarchs and popes.

This tool accepts either direction. Decimal input is validated to the 1–3999 range; Roman input is validated by re-encoding the result back through the canonical converter, which rejects non-standard forms like "IIII" (instead of IV) and "VV" (instead of X).