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Roman Numeral Converter

Convert numbers to Roman numerals or Roman numerals to numbers — the direction is detected from whatever you type.

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How to use Roman Numeral Converter — Numbers to Roman & Back

  1. 1Type a number, or type a Roman numeral — the direction is detected automatically.
  2. 2The conversion appears instantly, with a reference table underneath.
  3. 3Copy the result with one click.

About Roman Numeral Converter

Roman numerals are an additive system with one twist. Seven letters carry fixed values — I is 1, V is 5, X is 10, L is 50, C is 100, D is 500, M is 1,000 — and a numeral is normally read by adding its symbols from left to right, largest first: MMXXVI is 1000 + 1000 + 10 + 10 + 5 + 1 = 2,026. The twist is subtraction: in six pairs, IV, IX, XL, XC, CD and CM, a smaller symbol sits in front of a larger one and is taken away from it. That is the whole system, and the reason MCMXCIV looks harder than it is — read as M, CM, XC, IV it is simply 1000 + 900 + 90 + 4.

The half of the job worth caring about is the validation. Because each number has exactly one correct spelling, plenty of letter strings look like numerals without being one: IIII repeats a symbol four times, VX subtracts with a pair that is not allowed, IC tries to take 1 from 100. A converter that just walks the letters and adds or subtracts will happily hand back 4, 5 and 99 for those. This one converts your numeral back into its canonical form and only accepts the input if the two match, so invalid numerals are reported as invalid — which is what you want before carving a date into a slide, a plaque or a contract.

In practice you meet Roman numerals in a fairly small set of places: clock and watch faces, the front matter of books, copyright years in film and television credits, monarch and papal names, Super Bowl numbering, outline headings, and the occasional building inscription. All of those sit comfortably inside the 1 to 3,999 range this tool supports. Above 3,999 the traditional answer is an overline meaning "multiply by a thousand", which cannot be typed reliably as plain text, so the tool stops there and says so rather than inventing a notation nobody uses.

Frequently asked questions

Why is 4 written IV and not IIII?
Because Roman numerals use subtraction in six specific pairs. A smaller symbol before a larger one is taken away instead of added: IV is 5 minus 1 = 4, IX is 10 minus 1 = 9, XL is 50 minus 10 = 40, XC is 100 minus 10 = 90, CD is 500 minus 100 = 400 and CM is 1000 minus 100 = 900. Those six are the only allowed combinations, which is why no symbol is ever repeated four times in a row. (Clock faces are the famous exception — many really do print IIII for 4, purely for visual balance.)
What is the largest Roman numeral, and is there a zero?
The largest number with a standard plain-text spelling is 3,999 — MMMCMXCIX. There is no symbol for zero at all; the Romans had no need for one in a system that was built for counting and tallying. Larger values were written with an overline meaning "times a thousand", so V with a bar over it is 5,000, but that notation has no single agreed plain-text form, so this tool accepts 1 to 3,999 and tells you when a number is outside that range.
Is IC a valid way to write 99?
No. Only I before V or X, X before L or C, and C before D or M may subtract, so 99 is XCIX — ninety (XC) plus nine (IX). This tool converts your numeral back to its canonical spelling and compares the two, so IC, VX, IIII and other invalid strings are rejected with an explanation instead of silently returning a number. Many converters accept them, which is how a wrong numeral ends up copied into a document.
How do I write a specific year in Roman numerals?
Type the year and read the result: 1994 is MCMXCIV, 2026 is MMXXVI, 1888 — the longest year numeral of the modern era — is MDCCCLXXXVIII. Years are the most common reason people need this, usually for film and television copyright lines, building inscriptions, or the tail end of a credits sequence. Any year from 1 to 3999 works.
Can I get lowercase numerals like i, ii, iii?
Yes — tick the lowercase option and the numeral is written in small letters, the form used for page numbers in a book's front matter and for sub-levels in outlines. Input is case-insensitive in both directions, so mcmxciv and MCMXCIV are read the same way, and the symbol-by-symbol breakdown follows whichever case you have chosen.
Is it free, and is it accurate?
It is free, needs no sign-up, and runs entirely in your browser, so nothing you type is sent anywhere. On accuracy: every number from 1 to 3,999 was checked to convert to a numeral and convert back to the same number, with no mismatches, and the conversion code is covered by unit tests. The subtractive-pair table on the page is generated by the same code that does your conversion, so the reference and the result can never disagree.