Convert between a number (1-3999) and a Roman numeral in either direction with instant detection and a panel showing each symbol used.
All calculations happen locally in your browser. Nothing leaves your device.
Type either a number (1–3999) or a Roman numeral (M, D, C, L, X, V, I in any case) and the converter detects what you are typing, then shows the other representation instantly. Below the main result, a breakdown panel shows exactly how many of each building block — M, CM, D, CD, C, XC, L, X, IX, V, IV, I — make up your number, because every number in the classic range has one and only one such decomposition.
Standard Roman numerals have no single representation for zero and use an overline (or a 5000-letter bar) for numbers above 3999. This tool covers the classic range 1–3999, which is exactly what every school exam, clock face and chapter numbering uses.
When a smaller symbol is placed before a larger one, it is subtracted: IV = 5 − 1 = 4, IX = 10 − 1 = 9, XL = 50 − 10 = 40, XC = 100 − 10 = 90, CD = 500 − 100 = 400, CM = 1000 − 100 = 900. The converter expands your number into the largest symbols first and uses these pairs wherever they are shorter.
Every number from 1 to 3999 decomposes uniquely into the seven building blocks M (1000), CM (900), D (500), CD (400), C (100), XC (90), L (50), X (10), IX (9), V (5), IV (4) and I (1). The panel shows how many of each block your number uses, e.g. 1994 = M + CM + XC + IV.
Yes — the converter is two-way. Type digits and you get Roman numerals; type Roman characters (M, D, C, L, X, V, I, in any case) and you get the number back. The input is detected automatically as you type.
No. The whole tool is a few lines of vanilla JavaScript running in your browser. Your input never leaves your device, and there is no account, no tracking and no network request attached to a conversion.
If you just finished with Roman Numeral Converter, the natural next steps are Text Case Converter, Number Base Converter, Unit Converter, or browse every tool in Daily Tools.