quialo.

Roman Numeral Converter

Enter a value above to see the conversion.

Convert any whole number from 1 to 3999 into a Roman numeral, or turn a Roman numeral back into a number. The tool uses standard subtractive notation (so 4 is IV and 1994 is MCMXCIV), checks that your number is in range, and flags malformed numerals like IIII or VX instead of guessing.

How to use

  1. Pick a direction: number to Roman numeral, or Roman numeral to number.
  2. Type your value into the input field.
  3. Read the converted result, which updates live as you type.
  4. Use Copy to grab the result, or Swap to flip the direction and convert it back.

Examples

  • Number to Roman: 1994 becomes MCMXCIV.
  • Roman to number: LVIII becomes 58.
  • Largest value: 3999 becomes MMMCMXCIX.

FAQs

What range of numbers does it support?
It supports the whole numbers 1 to 3999. Standard Roman numerals have no symbol for zero and no agreed way to write 4000 or higher, so values outside this range are rejected with a clear message.
Why is a numeral like IIII or VV reported as invalid?
Those break the rules of standard Roman notation. A symbol like I, X, C, or M can repeat at most three times, and IIII should be written IV, while VV should be X. The tool only accepts well formed numerals.
Is the input case sensitive?
No. You can type mcmxciv or MCMXCIV and both convert to 1994. Surrounding spaces are ignored too.
How is 4 written, as IV or IIII?
As IV. The tool uses subtractive notation, so 4 is IV, 9 is IX, 40 is XL, 90 is XC, 400 is CD, and 900 is CM.
What does the Swap button do?
It flips the conversion direction and feeds the current result back in as the new input, so you can round trip a value and confirm it converts cleanly both ways.

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