Roman Numeral Converter
Type a number or a Roman numeral — get the other instantly, with the breakdown.
Standard letters I V X L C D M cover 1–3,999; a vinculum (overline ×1,000) reaches 3,999,999.
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How do Roman numerals work — what do I, V, X, L, C, D, M mean?
Each letter is a fixed value: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1000. You add letters from largest to smallest (MMXV = 2015), but when a smaller letter sits before a larger one you subtract it — this is subtractive notation, which gives IV = 4, IX = 9, XL = 40, XC = 90, CD = 400 and CM = 900. This Roman numeral converter builds and validates every numeral by those exact rules.
Why is there no zero — and no negative or decimal Roman numerals?
The Roman system has no symbol for zero and no way to write negative numbers or fractions of a unit, because it was made for counting and tallying rather than place-value arithmetic. So the smallest value you can convert is 1 (I). Enter 0, a minus sign or a decimal point and the tool tells you clearly instead of silently guessing.
What is the largest Roman numeral — can I go past 3,999?
With the standard letters the practical maximum is 3,999 (MMMCMXCIX), because there is no single symbol larger than M. To write bigger numbers, scribes used the vinculum — an overline that multiplies a numeral by 1,000. This converter uses vinculum notation to reach 3,999,999, so 5,000 becomes V with a bar (V̅) and 1,000,000 becomes M with a bar (M̅).
How do I write a year or date in Roman numerals?
Convert the whole number: 2026 = MMXXVI, 1994 = MCMXCIV, 2000 = MM. That is exactly how years appear on clock faces, building cornerstones, book chapters, movie and TV copyright credits and the Super Bowl (Super Bowl LVIII = 58). Type the year on the Number → Roman tab and copy the result, or paste a numeral on the Roman → Number tab to read a date you found.
Is my input sent to a server?
No. Every conversion runs entirely inside your browser in plain JavaScript — nothing you type is uploaded, logged or tracked, and there are no ads. Once the page has loaded it even works offline, so you can convert Roman numerals privately with no connection at all.