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Roman Numeral Converter

Convert whole numbers from 1 to 3,999 to Roman numerals and Roman numerals back to numbers.

What this tool does

Convert whole numbers from 1 to 3,999 to Roman numerals and Roman numerals back to numbers. You fill in these fields: Convert and Value. It shows roman numeral and number.

Inputs

  • Convert: Switch between: Number to numeral, Numeral to number.
  • Value: Text, up to 200 characters. A whole number from 1 to 3,999, or a Roman numeral such as MCMXCIV.

Worked examples

Example 1. Inputs:

  • Convert: Number to numeral
  • Value: "1994"

Results:

  • Roman numeral: MCMXCIV
  • Number: 1,994

How this is worked out: Standard subtractive notation: 1994 = 1000 + 900 + 90 + 4 = M + CM + XC + IV = MCMXCIV.

Example 2. Inputs:

  • Convert: Number to numeral
  • Value: "3999"

Results:

  • Roman numeral: MMMCMXCIX
  • Number: 3,999

How this is worked out: 3999 = 3000 + 900 + 90 + 9 = MMM + CM + XC + IX = MMMCMXCIX, the largest standard numeral.

Example 3. Inputs:

  • Convert: Numeral to number
  • Value: "MCMXCIV"

Results:

  • Roman numeral: MCMXCIV
  • Number: 1,994

How this is worked out: M 1000 + CM (1000 - 100 = 900) + XC (100 - 10 = 90) + IV (5 - 1 = 4) = 1994.

Example 4. Inputs:

  • Convert: Number to numeral
  • Value: "1"

Results:

  • Roman numeral: I
  • Number: 1

Limitations

  • Standard numerals only: forms such as IIII, VX or IC are rejected.
  • Whole numbers from 1 to 3,999 only.
  • No overline (vinculum) notation for numbers above 3,999.
  • There is no zero in Roman numerals.

FAQs

Q: How do I read a Roman numeral?
A: Add the values of the symbols from left to right: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1000. When a smaller symbol sits before a larger one, subtract it instead, so IV is 4 and XC is 90.
Q: Why does the converter reject 4000 and above?
A: Standard Roman numerals stop at MMMCMXCIX (3,999), because a symbol is not repeated more than three times in a row. Larger numbers need a bar over the letters, which this tool does not support.
Q: Why is IIII or VX rejected?
A: The converter accepts only the standard form, where 4 is IV and 5 is never placed before 10. A numeral written another way is shown as an error instead of being guessed at.
Q: Can I type the numeral in lower case?
A: Yes. Lower case letters are read as upper case, and spaces around the numeral are ignored.
Q: Is there a Roman numeral for zero?
A: No. The Roman system had no symbol for zero, so the lowest value this tool accepts is 1.

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